The method to my madness...is the same a the "black-base" technique....black, then I mottle white, then thin layers of main color. This will give a somewhat blotchy apperence. I proceed with decals and washes. When all is said and done, when it comes time to do the final dull coat...I'll spray the whole thing...then I'll add a little bit of white or light tan (depending on the main colors...white for grey finishes...tan for green finishes), to the dull coat (I am using lacquer clear with enamel paint). The "color" will build up very slowly and is very forgiving. Adding just a little color to the clear helps keep a good spraying consistancy, so it doesn't have to be so thin. Whenever I have tried using very thin paint, I end up with tiny spots and inevitably, I'll end up pushing the trigger a bit too hard and end up with a nasty blemish.
I use the same method (adding dark grey/black/brown to clear flat) to do exhaust staining.
Like anything, try it out on some scrap or "paint mule"