This instructable is to show how to get a (hopefully!) show car finish with a candy finish. I'm posting it as I go (the step with >>> in front of it is where I'm currently at), so let me know if you see that I'm fixing to do it wrong! Also, since this is a live instructable, I'll be uploading videos on different parts once I edit out the cursing...

Stuff In The Works:

Picture of blocks and their relevant surfaces
Videos of the sanding motions
Everything after blocking...

So hopefully, Instructables will let me edit this as time goes on!

This is using 2k urethane car paint... originally this was going to be a Summit Racing paint job, but Alsa had a sale on their base & clearcoats the other day, so I switched to them.... Hopefully it's a change for the better!

Materials:

1932'ish Ford Model A Replica (Glassic Motorcars S/N 1120)
Lots (4 gallons so far) Laquer-based sandable primer
4 cans so far spray-paint sandable primer for a guidecoat
1 Gallon Bondo Plastic Filler
1 Gallon 2K Primer/Surfacer [APS-2712]
1 Gallon Nevada Silver Stylin Basecoat [ASB-01]
2 Gallons Speed Clear [SC1230G]
8 oz Cobalt Blue Candy [CB8]
4 oz Black Candy [BK4] (I'm hoping to mix this with the CB8 to get a navy blue for the bottom half)
Striping tape

And tools:

Pressure Washer (strike that!)
Durablock Sanding Blocks
Hard Plastic Sanding Block
PSA Sandpaper in 180, 320, and 1000 grit
HVLP Spray set from Amazon - It seems to be better than the Harbor Freight HVLP I was using... but the Harbor Freight gun isn't too bad once you clean and fix it
Paint gown and Respirator
Water

Let's start by stripping the car!

Step 1: Starting Clean

It's important to start with a clean surface... in my case, the original paint was heavily orange-peeled and flaking off in places, so it had to go. For those with still-good-factory finishes sand with 800 grit sandpaper (or Red Scotchbrite) and jump to the Applying Primer section.

Because I saw the paint was loose, I thought to myself "let's use a pressure washer to make short work of it." Bad idea. My car is fiberglass, and it turns out that there were several "loose" or "not solid" spots in the 'glass!

After that, I patched some places with plastic filler and proceeded to sand the car the rest of the way -- down to the light-blue gelcoat. It turns out that the original paint was on-top of a waxed paintjob -- and they didn't scuff it (that's why it was flaking off!).

After you get the car clean (if you have a steel car, you can try "Aircraft Remover" -- warning - that's disgustingly toxic stuff so wear a mask, gloves, and disposable clothes -- but Aircraft Remover also removes fiberglass, so I couldn't use it).

On to sanding....

Step 2: Tips: Starting Clean

Aircraft remover does a good job stripping paint, filler, and everything else off metal. It kills fiberglass though.
A pressure washer shouldn't be used on a fiberglass car.
Make sure you go low enough (in my case, down to gelcoat -- past the waxed paintjob)
After scuffing, use a degreaser to make sure the surface is cleaned and doesn't have wax or grease on it.

Step 3: >>Leveling the Surface (Blocking, Sanding, Filling)... in General

Note well - these are my tips... if someone sees something amiss, please let me know. This step seems to take forever...

It turns out most of your time in a show-car paintjob will be spent blocking and straightening the body. Painting is surprisingly little time.

My process has these goals:

Minimize buildup (my car is flexible... 1/2" Bondo all the way around probably isn't -- and sheetmetal is also flexible in some areas, so minimize cheating)
Get back to painting faster (if you're not putting things on, you're not going forward)
Ending up with a nice, straight car (no shortcuts)

So, let's get started...

Step 4: Levelling the Surface: Initial Primer

Initial Etching Primer Coat

For metal cars, you need to put down an Etching Primer coat that will bond itself to the metal and prevent water from getting in and rusting. Sadndable primer and plastic filler are porous; they'll let water in underneath them and let the rust start eating away at the body. If you're doing fiberglass... you don't have to worry about that. Make sure the metal is warm or you'll trap water under the Etching Primer and rust will still come! Then, after it's flashed/cured/whatevered, go to the Initial Sandable Primer Coat.

Initial Sandable Primer Coat

Spray the initial primer coat on in this sequence:

1 Light coat to wet things (supposedly prevents runs)
3-4 Heavy/Wet coats, wating the "flash time" between coats
Wait the "flash time" before you dust with guidecoat

Flash time is how long the solvents take to evaporate out. If you don't wait the required time, you end up with "solvent pop" as the solvents work their way out through your finished paint job (ick!).

Step 5: >>Levelling the Surface: Guidecoat, Blocking, and Primer... Repeat As Necessary

Guide coat is a light dusting of color on your primer that lets you know when to stop. Some people say you have to use the dry guide coat ($30 for a kit), others say you can use any paint. I compromise -- I use Spray Sandable Primer. That way it doesn't cost much, and the Sandable Primer doesn't gum up your sand paper like a Krylon can would.

Pro-Tip: Use a color that doesn't match anything you want to keep. And have it not be the same as your filler that your sanding. For example, if your base primer is gray, but you've used black epoxy to cover pinholes, you should use red oxide for the guide coat.

Blocking

Blocking is the process of using sanding blocks to even out the surface. You never want to sand with sandpaper on your hands because that will put gouges in the paint where your fingers are. You also never want to sand with sponges because they will follow your surface and sand the dips just as well as the high spots.
I sand until you get 2 "high spots" on the panel... one high spot means that you can still sand more; sand "more" away from the spot (eg, block twice to 3 times as much away from the spot). when you have 2 high spots, the rest is low, so add more primer. If you're able to sand the guidecoat away and not break through the primer, you're done with blocking (yay!)! Go to the Painting step!

If you "broke through" or "showed high" in any area (even Bondo... the activator in Bondo can discolor your base paint job), you need to add another layer (that layer can be the sealer coat if you're confident that there's no filling left). If it's "only a little," you might want to skip the whole high/low coats thing and just put on 2 full coats.

Adding The Next Layer: Bondo

When adding another coat, first see if you should be using plastic filler (eg, Bondo) instead. Bondo is thicker and can be pressed into crevices. Due to its short working time (7-10 minutes) and my tendency to mix up way more than I need, I inspect the bodywork after blocking and make little "flags" out of the painters tape that indicate where Bondo is necessary.

Remember, the tube goes with the whole can... keep your ratios right. I found out that some Bondo palettes have a color chip that is your target color... Sweet!
When mixing and applying Bondo, use firm scraping motions instead of a "kneading" or a "chopping motion" because you don't want to mix air bubbles into the mix (air leads to pinholes. Pinholes lead to suffering).
When it starts to harden on you palette, do not apply any more to your surface... the curing process has started and if you try to apply it, you'll get a cottage cheese finish.
About 1 minute after curing has started, you should go around to all the places with a razor scraper and get rid of the "mistakes and drips" so you don't have to sand those out later.

Bondo is harder to sand than primer, so I recommend going over the spot with a hard block. If you do this quickly (within the first couple of hours after application), Bondo will gum up your sandpaper...

Then go to primer, treating the Bondo'd area as a "low spot".

Adding The Next Layer: Primer

To build up the lows faster and get done faster, I follow this pattern (please tell me if I'm doing this wrong!):

Paint the lows 3 times (if I can remember them after the first coat!)
Paint the grays twice (which adds another 2 layers to the lows)
Painting the whole car twice (so the lows now have 7 layers)

Remember to wait the flash time between coats! Doing it this way, you only have a few coats on the high spots, so if the lows haven't come up enough, the high spots will "show high" quickly. Wipe the car/panel down with lacquer thinner and a microfiber rag to get rid of any dust left over, and paint as above... and back to guidecoat for another round.

Go back and add your guidecoat and start blocking again. And again. And again.

Step 6: Tips: Blocking/Sanding

Do:

Start each day with fresh paper (you can't put PSA paper on during the day if you're using water)
Long blocks are faster and prevent waves
Hard blocks get rid of bumps faster but tends to flatten curves -- but they are the key to sanding down plastic filler (plastic filler doesn't sand as well as primer, so a hard block hits only the high spots)
When applying paper to the blocks shift it slightly so there's a "safe edge" (no paper)
Wet sanding keeps the dust down and keeps the paper fresher than sanding dry
Scrape up mistakes after Bondo with a razor blade
Sand Bondo using a very hard block
For curved surfaces, try using a paint stirrer or a rubber hose. Don't use on flat panels though!
Don't use a very hard block on the curves... it will flat-spot them -- The Durablocks seem to be a great compromise
Use the primer steps as practice for painting the car (it helps to have a friend ~12 feet away because they can see the wet edge better than you can since you're so close)

Don't:

Use paper on your hands; always use a block of one kind or another
Use sanding sponges
Use a block that is too small (shoot for at least 25% of the panel's length or longer)
Use a hard block on round corners (it will flat spot them)
Work air into your Bondo
Keep applying Bondo after what's on you palette starts to cure (gets grainy)
If the scraper is having a hard time with the Bondo, you gotta stop and sand instead. You'll end up pulling the Bondo away from the surface

Step 7: Painting...

When you get your paint, double check it:

Make sure you got what you ordered -- on mine, I got Jet Black instead of Silver (Not looking for ghost effects, so...)
Make sure have the right ratios of ingredients -- each layer may have its own thinner / hardener
Make sure you have all the pieces before you start -- with a 2k urethane job, after the cure time is up, you have to scuff the pain job if you want to add another layer or it won't adhere
Make sure you have the proper safety equipment!
Take all the paint and put it in a climate-controlled environment -- if it freezes, it's useless.

General Approach

Timeline:
1. You can't sand metallics/pearls. If you do that, it won't look right
2. You must wait for the clear to cure before sanding
3. You must wait the flash time (or 2x the flash time if doing many layers) between coats
4. You must put the next layer on within the recoat window, or they won't be able to chemically adhere
5. Always "move the wet edge"
6. Never start/stop on a body line or a panel line -- this will cause buildup where you stop/start. Never stop/start at the same place for every coat for the same reason.
7. Be the robot.
Equipment Handling:
1. Keep the gun 4-6 inches from the body. Use the "wall of air" test to find the ideal for your gun
2. Keep the gun's fan perpendicular to the body panel
3. Remember, you can change the fan's orientation using the cap
4. Put the hose behind you and hold on to it with your other hand so you don't accidentally touch the panel
5. You might want to scrunchi your sleeves for the same reason
6. Once the hardener/catalyst is added, the paint will cure... on the car, or in your gun!
7. If a step has a hardener/catalyst, it has isocyanates and is toxic. Wear fresh protection!
8. Once unsealed, the activated carbon filters have a lifespan of only 48 hrs. After 2 days, you need new ones regardless of if you were painting or not.
9. Always unfold the tack cloth all the way and let it air out for 30 seconds before using
Material Techniques:
1. Water isn't as much of a problem with 2k as it was with Laquer
2. Silicones are always a problem and will cause fisheyes. No WD-40 on anything!
3. You need to stay above 60 degrees for the paint to cure (Alsa paints anyway)
4. Some basecoats (like my Nevada Silver) have no filling ability. Final sand must be >1000 grit!

Step 8: Paint Prep!

Make sure you have ventilation
On fiberglass go over with a light spritzing of alcohol+water and a microfiber cloth. This cuts down on static electricity.
Go over your car with a tack cloth
Wet down the floor (humidity doesn't make 2k blush, and your floor is dusty; making it damp keeps the dust on the floor and off your paint)
Know that overspray is going to go everywhere. If you're in your garage, clean out anything you don't want overspray on (other cars, milling machines, etc). HVLP helps. But not that much!
Wear a paint gown to keep this poison off your skin.
Wear a fresh respirator to keep it out of your lungs
Know the temperature for your paint. My paint has to stay above 60F for the entire cure duration.
This is flammable! You can't cheat the above with a propane heater!
Know your chemicals! Each coat may have a different hardener/activator/reducer/catalyst. Mix these up and the paint won't cure
Know your ratios! Each coat has a different concentration...
Draw a line through the adjacent areas on a paint cup so you don't accidentally read the wrong line

Step 9: Sealers and Basecoat

Since my basecoat doesn't fill in scratches at all, Alsa recommends putting it wet-on-wet over a sealer coat of their 2k primer. If not done wet-on-wet, scuff the paint with 1000 grit so there will be some mechanical adhesion. Other paints are more tolerant and can handle 400-800 grit as the final sand...

For my base (Nevada Silver, ASB-01) as well as most basecoats, you want:

50% Overlap
Mixed 1:1 with the reducer (so I effectively have 2 gallons of the paint) -- note that's specific to ASB-01!
2-3 coats to make it opaque, waiting the flash time between each coat

Check you chemicals! If your basecoat has a hardener or a catalyst in the reducer it has isocyanates in it and will poison you. Not to mention, it will start to cure when mixed -- in your gun, in the can, wherever it was mixed.

Step 10: Painting Art

If you put the art underneath the final clear, you don't have to worry about the buffer lifting an edge and destroying it. If you're gutsy, you could apply the artwork directly on the base, but remember: you can't sand a metallic or pearl, so if you mess up, you have to redo the entire base, so I (and others!) recommend putting down 2 layers of clear and letting that fully cure before laying down art.

Then you can scuff the entire area you're going to clear after graphics (any time you let the paint cure you must scuff the car because you're depending on mechanical adhesion to hold the paint on the car instead of chemical adhesion; in my case this is the entire car because I want non-candied strips and a candy paint job), and lay out graphics/stripes/etc. That way if you make a mistake, you can wipe it off with lacquer thinner or sand it off and be ok since you didn't sand the basecoat and disturb the peals and metallics.

Step 11: Candy and the Clearcoat

The color in a candy finish is a tint that's added to the clear. OT1H, you get a beautiful deep sheen of color. OT2H, since all the layers are transparent, if you make a mistake anywhere in this process, you're going to see it.

Recommended steps (from youtube videos):

Light coat to make a wet surface (75% overlap, finer spray)
1-2 Light coats to make sure it's wet (75% overlap, finer spray)
2 Heavy coats to get all the color on (50%-75% overlap so you don't get zebra stripes)
Keep a wet edge (especially since Alsa speed clear has a flash time of only 15 minutes and a cure of 2 hrs)
Be the robot.

After you're done with the Candy stage, go back and add 2-3 coats of plain clear. This provides UV protection for your candy tints and gives you something to color sand later. Remember the flash times and recoat windows!

Step 12: Color Sanding

After you're done with the clearcoat stage, you'll see slight orange peel (how slight depends on how well you gun was set up and your technique). For a show-finish, you need to "Color Sand".

Despite it's name, Color Sanding is actually only sanding the clear -- if you get down to your base, you've gone too far and need to scuff and re-clear the panel.

Getting Rid of Imperfections

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Getting Rid of the Orange Peel

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Adding a Flow Coat

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Buffing to Perfection

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Wait! Don't Wax Yet!

Despite Having Cured, the paint has a lot of chemicals that take longer to escape. Wait 30 days of being in the sun (hopefully driving your nice new car) before washing and waxing.