Okay, I'm going to give up one my secrets
Miller,
This what I do to get a nice hard edge camo with an airbrush. I use Tamiya acrylics for airbrushing thinned w/rubbing alcohol. - I can't sat if this will work with any other set-up
1. shoot colors for scheme - allow overlap and a flaired edge do lightest color first and then move to darker
2.Use the thinned down paint mix that you just shot through the airbrush and hand paint the outline of the camo colors -definetly using the darker color as the overlap. Use quick smooth strokes. The paint is thin so it flows smooth. Because it is thinned the thinner will actually cut away some of the overlap allowing a nice blend.
3.You will get a slight hazing in the areas where you hand paint. Don't be alarmed. First coat of flat overcoat makes it disappear.
4.Touch-up if necessary.
Hope it works out.