Thanks all!

big honkin jeep: Denatured alcohol never really cut the mustard for me as a degreaser. It's a great drying agent, but it pales in comparison to mineral spirits and naphtha for degreasing wood and acetone/brake cleaner for metal. I've never had a problem with those other solvents disturbing injection molded plastic stocks. I think nylon is pretty inert in that regard. I have heard about stronger solvents eating away certain plastics. For example, I know the active ingredients in the brake cleaner I use are acetone and toluene. Both are known to attack Kydex (which is a combination of acrylic and PVC), but the exposure is so limited there's no damage. And the finish holds up fine, too. The cheekpieces I've painted are still looking good, despite being subjected to my face grease and weekend stubble.

Health hazards are another thing, and I take it seriously. The light blue gloves I use in the video are fine for the limited exposure to solvents in this application, but when I'm using acetone, I'm wearing heavy nitrile gloves. That stuff eats the light duty gloves for breakfast.

Nic: The technique is super easy to do. Within my first few dabs on the practice stock, I had a good feel for how much pressure to use to get the desired blotch of color.

30-06: I found synthetic sponges with finer, more uniform foam structure (like those used for washing cars) leave a more solid blotch of paint. I experimented with one, trying to get a good tiger stripe pattern, but I was never pleased with the outcome. I will say I like tiger stripes to break up the outline of a gun. I did them on my Taxis project, and just by looking at it you can see how the camouflage effect is working.