Jim,
I used Gunze Sangyo Aqueous acryllic colors. The airbrush is a Badger 100 (extra fine head). Typical pressure is around 10-20 psi. The sharper you need the camo demarkation to be, the lower the psi. I also typically use a 50 - 50 thinner to paint ratio although I'll get the paint portion higher if I'm trying to cover a large area and not get fine.
Good luck! Sorry for taking so long to reply. It took me a while to get set up on the ARC discussion forums.
Sam