If you are looking yo do the sort of German 3 tone camo four tips I have found invaluable.
1.) Keep pressure down 10-12 psi if possible
2.) Get a good 2 or 3mm needle
3.) Make sure you paint is thinned to milk consistency
4.) Be prepared to go over the edges of the camo with the base colour again to tidy it up - its worth the effort.
Cheers and good luck
TT