Great job, Bryan! Can you elaborate how exactly you went about painting it? Do you use a primer? Do you spray paint? I think that the boxes look brilliant!
It's a lot of intricate masking tape work. First I take it apart as far as I need to. Remove the metal front lens/viewfinder plate, take photos of how everything will need to go back together. It's quite simple but there are some parts that can go in two different ways. If you have the older non-flash model the name plate on the front unscrews so you don't have to mask that. On the flash models it's riveted so you have to mask it. The metal film wind knob also unscrews on the non-flash model.
Next I remove the film holder which also holds the lens in place. It's just two screws, very simple. Some people remove the shutter and buttons but this gets more complicated and is necessary unless you want to paint the buttons. The buttons have a fairly tight tolerance, I would worry that the paint will make them rub and interfere with use. On the film holder you took out there's a metal tab on the feed reel side that prevents a larger 120 reel from being used, Bend that until it breaks off so you don't have to re-spool onto 620 reels, you will still need a 620 take-up reel. Also, note which way the lens is facing, the tapered side of the plastic housing faces the film, you can flip this when you put it back together.
On the back part of the body the only thing you can remove is the latch/strap holder. There's a retaining ring on the inside of the chamber, you can push this off with a large screw driver, be careful not to slip and damage anything. Note how it all goes back together. The back of the strap is riveted so that will need to be carefully taped up. Also the red window will need to be carefully taped, also be careful when removing the tape, it's easy to damage the red window.
Before any taping I clean the camera really well. I use Dawn dish soap and water then quickly dry everything. This removes grease and dirt really well. Get into all the little nooks and crannies. The problem with Bakelite is it doesn't do well getting wet, it can start to swell and the finish can get ruined. That's why you need to dry it quickly. If you use rubbing alcohol do it quickly and stop, this can destroy the finish if you do it too much.
On both body pieces I tape everything that I don't want to get paint on. This includes the groove parts where the two halves go back together. Also where the latch rubs against the plastic on both halves of the body. If you don't tape that it will be hard to open and close the camera. On the front half I tape up the buttons and knob and the front where the metal plate came off. Also the name plate and the flash buttons. Get a good brand of tape, 3M or Scotch, the cheap stuff either doesn't stick well or can be difficult to remove.
For all the detailed taping an Exacto knife and a tooth pick come in handy for cutting and pressing little bits of tape into small crevices. After all the detailed stuff is taped I run some wide masking tape across the openings of the two halves to seal them off.
A primer coat will help make the paint stick much better, less chance of chipping off. Some paints say they are paint and primer in one but a dedicated primer coat is better. I usually do two light coats of paint followed by a clear coat when I am happy with the coverage. Let it dry at least 24 hours before you take the tape off and put it back together, the paint will be soft and easily damaged before that.
When it comes to choosing colors, I let my wife do that, she's much better with things like that.