Mike - thanks a lot, and I appreciate it! My goals were to fit the figs to the model, so that they don't look "floating", and at the same time to avoid seeing "the same guy" on every model I do - there aren't this many Vietnam War figs around. Congratulations on your figures!
Gamera - so you're already into modifying figs! You're doing great! I especially like the tanker boys. When you say faces are tough, girl's faces are a lot tougher still, IMO.
As for painting those faces I'd like to mention two things, maybe thay can help somebody.
First would be to avoid pure black and white on the face, especially the eyes. If you use dark grey and light grey instead, it's easier to avoid that "horror stare" on the figs, and the face looks better IMO.
Second thing, that was suggested to me by ajlafleche, was to only paint the lower lip, and rather use dark brown than some pink/red hue here - helps to avoid that "lipstick" look.
I hope this helps somebody, thanks for reading and have a nice day
Paweł