This technique works for just about anything--furniture, automobiles, guitars, etc.
For large projects (cars), power sanders and buffers are helpful. But for small things, it's great. And for beginners, hand-sanding and rubbing is less likely to burn or sand though paint and clear--it's a safer route...
Hey--it's a bit intimidating at first, but really not that difficult (with the right supplies.)
This example is a vintage thin-line hollow-body guitar that needed several structural repairs....
Step 1: Supplies
1) Rags. Lots of rags.
2) Wet/dry sandpaper-- 400 or 600 grit to start, 800, 1000, 2000 to finish.
3) A sponge for a sanding block.
4) A bucket of soapy water.
5) Rubbing compound.
Rubbing compounds and fine sandpaper can be found at automotive supply, home improvement, or craft stores.
Important Note: Avoid any rubbing or polishing compounds that contain silicon. It may look pretty, but any subsequent painting will be a nightmare!
6) Jewelers Rouge (or "polishing compound")
(ible user Spokehedz indicates that block polishing compounds like Jewelers Rouge are available at Home Depot. Any real hardware store is also a good source.)
Step 2: Getting Started
And for smaller objects, a workspace is required. Even for cars, this should be done indoors.
I used a old workmate portable bench, and covered it with old towels. They help stabilize the work, and prevent scratching.
After this piece was repaired, it was sprayed with lacquer (five coats.) The resulting finish is a semi-gloss with a fair amount of pebbling and orange-peeling.
Lacquer should be allowed to dry for several weeks, but you can work with it sooner. Don't, under any circumstance, use any masking tape on fresh lacquer, even the blue "easy release" tape. You'll have to start all over...
These techniques aren't limited to lacquer, of course. Acrylic paints, urethanes, etc. will work just as well (and not have the long drying time of nitrocellulose lacquer.)
Step 3: Initial Wet Sanding
Soak the sandpaper in the soapy water. Use your sponge as a sanding block. I cut this small one from a larger sponge, and this is one of several cut.
Use 400 or 600 grit wet-dry paper. Be especially careful during this step, as sanding through the finish is easy with the coarser paper. Preparation (sanding, filling, painting), and multiple coats of lacquer help to insure the finish is free of woodgrain texture. If grain remains in the piece, sand with the grain.
Exercise care when sanding hard edges. It's very, very easy to cut right through the finish on a corner.
Wipe the work down often, first with a damp cloth, then a dry one. Inspect visually. This will help gauge your progress.
Sand only until any uneven surface texture is removed.
Note:If you drop the sponge, sandpaper or wiping/drying rag on the floor, START OVER WITH A FRESH SPONGE, SANDPAPER, ETC.
You're likely to scratch the work, if you don't.
Step 4: Finish Wet Sanding
This removes any scratches incurred in the rougher sanding stages, and assures a smooth base for the high-gloss finish.
Inspect the work visually, but also be aware of the tactile 'drag' you feel while sanding. If it's not consistent, be sure the piece is wet overall, and check the feel again. Spend a bit more time gently sanding the 'dragging' spots. If it continues to drag in areas, then moving back to a coarser grade (from 1000 to 800 grit, for instance) might be called for...
Cycle through 800, 1000 and finally 2000 grit paper. All steps are wet sanding. A gentle, circular sanding motion is fine. However, if any woodgrain texture remains, best to sand with the grain.
Step 5: Rubbing Out
A rubbing compound is now applied. Use a soft cloth--an old tee shirt works well, or a terry cloth towel.
Apply a small amount of compound to the cloth ('charge' it), don't try to rub out the whole piece at once.
Work the compound into the surface evenly. As it begins to thin and dry, you'll feel more resistance. Continue to rub. You must rub the compound dry, and off the surface for the full effect. Turning the cloth (to where it's clean) near the end of the 'charge' will help complete the rub, and remove any remaining compound. But don't work with a clean part of the rubbing cloth until it's nearly all rubbed out.
The rubbing compound should include instructions, as well. Follow them...
Step 6: The "Big Finish"
For a final step, I used a bit of jewelers rouge on a dry cloth.
Jewelers Rouge is a very fine abrasive, and kicks the shine up that last little bit. A "polishing compound" can be substituted here. These very fine compounds are the last abrasive step in the process.
After the abrasive polishing, I also apply a quality guitar polish, which is similar to furniture polish. It can add gloss and protect the finish, but doesn't remove any finish in the process. Be sure the polish is formulated for guitars, though.
Step 7: Addendum: the Guitar
It's just to show the finished, reassembled guitar. Very little work was done to the front of the guitar, just the back and sides. But it's very pretty, so I wanted to show it off. Plays nice, too.
The guitar is a late 60's Sekova thinline hollow-body electric. This is a MIJ (made in Japan) instrument. The company imported Japanese guitars into NYC, USA in the late 1960's and early 1970's. It's common heritage with Teisco and Kawai is pretty obvious, but they were allegedly made by Aria.
I'll quote some info from the 'net. I cannot speak to it's accuracy:
Sekova was a brand name for the Musical Merchandise Company of New York. These guitars were produced by ARAI whose parent company was ARIA. These well made copy guitars were more than likely built in the Matsumuko plant in Japan.