Ah yes, the painter frustration syndrome. We've all been there man - I'll see if I can help out a bit.
-Greens. Damn painting greens. I either get the highlights too stark, or so subtle it looks like there are none.
What sort of green are you going for? Could you give a example of the look you're trying to get?
My fleshtone. God damn that paint. It manages to be both too thick to paint on without brushstrokes being visible in it, as well as too thin to get decent coverage without a ton of layers. I thought I had a bad paint, and bought a new one. Same problem
My experience with fleshtones is that they in general are quite thick in nature. For smooth transitions you will need to have it thinned down, but not too much as in your instance. I usually go for 2/3 paint, and 1/3 medium when I'm painting fleshtones in general. This gives you a mix that can cover most things in 2 coats; 1st coat for transitions and 2nd coat for coverage.
What paints are you using for your fleshtones?