I have had great luck with thick, bushy makeup brushes when I use them to highlight up the colors on a dark base like that.
Perhaps start mixing in some Khaki and then Iraqi Sand and use those makeup brushes ($3-$5 each) to lighten that green. Then the detailing and stuff.
I just ordered 78 Vietnam minis from Empress. Someday, when I have a little more room, I'll make one of those fantastic Pibbers!