>> See Also: Arnold for Maya Tutorial Render Settings
I made various control maps(specular color,specular roughness,bump,etc) with mari and shading with arnold(alshader).
The cleaning of raw scan data,topolygy,detial sculpting and color maps were made by Jia Honglong who is a great supervisor in digital asset.
or Arnold for Maya Tutorial - Skin and Hair Shaders
if you want to learn about render Portrait in Arnold for Maya please check Lighting in Arnold for Maya Tutorial
More about Arnold