Hair system:

I selected the polygon hair mesh styled in Mudbox, isolated it in a layer and turned on the "Make Live" feature. I was now able to add more NURB curves that automatically snapped to the hair geometry. Then I selected all my curves and generated Paint Effects strokes from them.

It is now much easier to style our hair shape as we can now apply twisting effects, curling and other kind of Paint Effects function that are way harder to achieve with regular NURB curves.

Now I select all my Paint Effects strokes and converted them to NURBS. From this NURBS surfaces, I go to "Edit Curves->Duplicate Surface Curves" and hit the option box. In my case I only want to duplicate the U surface isoparms.

Now I have a set of new NURB curves derived from the outer edges of our NURB surfaces. The stage is now set to bring life to our hair, I create a little polyPlane far away from the main scene and created an nHair system. Then I simply assigned this nHair system to our newly created curves.

After having done some test renders and set up my hair system, I separated the hair system and applied a "SurfaceShader" to the head. I now have seven render layers with four render passes for each.