So, I have this head I am working on.

Now, I am having some problem with texturing. I am using zbrush and I see people create these amazing, realistic skin textures. And I am a bit lost as to how they manage to create these results. What are the techniques and so on. So far, I’ve just been doodling. Coating him with stock skin texture images and seeing what works (It doesn’t, is the brief version)
So, any help is appreciated. Any tutorial, guide, tip and such.