Tsubasa Nakai
CG director
man's portrait Breakdown
Here's the breakdown about skin shader and hair.
I hope it helps your work.
Feel free to ask me in the comment, if you have any questions.
resources for skin shader
https://www.youtube.com/watch?v=ss13J1emsvw
http://gl.ict.usc.edu/Research/DigitalEmily/
resource for hair shader
resources for xgen
https://gumroad.com/l/avAxQ
https://www.artstation.com/artwork/QBvGr
Xgen (hair)
Xgen (beard)
Xgen (eyebrow)