Necromancer by Mahhona

I use the Mixer Brush Tool  with these item : humidity 38%, charge 50%, Mix 32% Flux 41% to unify the skin and then I use the smooth round normal brush with the color of the skin to paint on it with 20 at 40% of opacity. After that I work on the shades and the lights to increase them. You can find tutorials about this technique on the Net that show you how to do Most of them use the smudge tool instead of the mixer brush tool but I prefer the mix brush tool. The surface blur filter can also help you to unify a little the skin. I guess there are different ways to do this, you have to find the best one for you The difficulty is to keep the shades and lights of the face so it still looks like a face and not just something flat without any form on it

I'm not a master in this technic and I still learn a lot about it but I hope I helped you a little to start with