I wanted a quick project I could do in just a day, so I dug out some old paintball guns and pimped one of them out. It taught me a lot about prop design so I thought I'd put together this instructable with a couple of tips you can use on your own projects whatever they might be.
The basis for this build was to make something that looks like it might fire incendiary rounds or a miniature flame-thrower, and also to experiment with weathering techniques. It was also important that this model was still strong enough to hold together with a bit of man-handling, since I'd like to actually use it in paintball.
Step 1: Adding Extra Parts
What I love most about this build is that it's held together with zip-ties and tape, which actually makes it a lot stronger than it would be if I'd have used glue, and still entirely usable. All of the additional parts are made from PVC tubing, wire and zip ties. I think it's really important that you aren't too precious with materials, and using whatever bits you can scavenge can actually add a lot of artistic depth, particularly since this build is designed to look ghetto.
PVC tubing is a staple in just about any build involving guns, because its cheap, strong, and paints well. It's also really useful in the way that it can be layered up by cutting it lengthwise and allowing it to bend and wrap over other parts. This is well illustrated in the barrel - notice how the small ring wraps over the end-piece giving the appearance of one solid piece of metal. I glued them all to the gun and then used zip-ties to reinforce various parts. Although cheap and nasty they really add to the strength and actually look like part of the gun on the finished model.
I also used electrical tape to secure the top pipe, which I later removed once the filler was holding it securely in place.
Step 2: Filler and Sanding
Normally I would just wait for the filler to set and then sand for hours on end until it's the shape I want, but this time I discovered from my impatience that you can actually use a knife to carve it when it isn't fully cured. After mixing you will have about 5 minutes to fill in the bulk of the shapes you are trying to make. Once you have your shapes bulked out, get off all of the bits you don't want ( this should be really easy because the filler should be starting to harden at this point). After 10-15 minutes your filler will be at the perfect consistency to shape with a Stanley knife or similar. You should be able to continue carving like this for at least 5 minutes, at which point it may become too hard to shape easily. I also added in the wire at this point and sculpted the filler around it.
You will probably want to add a few more coats of filler to get it fully smoothed out, using low grit sandpaper between coats. Once you are happy with it, work your way up the sandpaper grades to get a nice, smooth surface.
Step 3: Scars and Primer
It's important that you pay a lot of attention to the paintjob because it can ultimately make or break your model. Even if the modelling didn't go so well, you can make anything look good with a decent paintjob, for this reason it's necessary to rub down the entire model with a scotch-brite pad (you could use high-grit sandpaper, but scotch-brite pads are excellent at this) in order for the paint to adhere properly to the model. I used clear primer which I've never used before but actually worked really well. Shake the can really well and apply light, even coats.
After the primer I painted it grey for the metal, at the time I thought that silver would have looked better, but plain grey actually gave a really impressive effect and it made it look much more industrial and tough - like cast iron perhaps.
Step 4: Final Paintjob
Getting the Vaseline off was quite hard, as it made the entire model quite greasy, so you would be well-advised to use some turpentine. There isn't much technique to this, just use tissue and/or a sponge to wipe it all away.
I hand-painted the barrel and handle dark grey, then used some watery matt black paint which I put into some of the gaps and corners, using a sponge to make it look more organic and dirty. I then made some very watery browns, greens and reds and used a sponge to give the appearance of dirt, mud and grime. Be careful not to overdo this step, it's a very easy mistake to make. Finally I used some silver paint and with only a very small amount on my brush I gently went over the edges of the black parts to give the impression of worn metal. This is particularly effective around the barrel.
And finished! I can also say that it still fires perfectly well, and is incredibly sturdy.