When doing something like this, don't forget to set the gamma value for the normal map to override: 1.0. You'll have to do this for the specular and displace maps too. To tune the normal bump intensity, first, use a standard material. This goes faster than the sss to render. You can also leave the subdivision levels of the Turbosmooth modifier to 1 or even turn it off, since your bump and displace are independent (one other advantage of this technique.
Next I placed a couple of directional lights, with very sharp shadows (raytraced shadows, of course, and a small area size). I turned the mr photographic exposure control on, tuned it, placed a camera and then hit render. To get something close to what I wanted, I used the scale conversion factor (Fig.26). I didn't need to use individual channel adjustments, as mr sss2 has good default settings that needed just a little tweaking (Fig.27).
Once the scale was OK, I started playing with the individual RGB parameters of each layes, to see how it influenced my shader at rendering. You can get some quite interesting red color bleeding in the areas where light meets shadow if you keep using values that are multipying by 2 from right to left (e.g., 24, 12, 6 or 8, 4, 2).
I used the same values for the last two channels (green and blue). Then I plugged my diffuse map into the epidermal and subdermal channels (one cool thing about this new sss2 is that I didn't use a different map for the epidermal and subdermal channels, since you can control the RGB amount directly by tweaking the shader values).
I set the unscattered diffuse weight close to 0, since it only attenuates the scattering effect (you can use it for make up or body painting, for example). Then I tested it until the result suited me.
Fig.28 shows some late shots I rendered during the testing phase. I felt then it was OK to move on to the final render.
As you can probably understand, this stage took quite some time. Here is a screenshot of my SSS tunings (Fig.29), but keep in mind that all these values are pretty worthless if taken "as is” to your own model. Might be helpful anyway to give an idea of how my shader was done.
For the hair, eyebrows and beard creation, I imported my base mesh once again. I selected faces and detached objects to make "scalps”: one for the hair, one for the beard, and one more for the eyebrows.
I also made some hair for the pullover.
I painted a black and white map to be used as a length map (basically, black areas will have a hair length of zero, while white ones will have full length. You can play with shades of gray too to get intermediate length)(Fig.30)