After setting my lights with a basic override material, I started creating the main SSS. Instead of using the FastSSS2 I went for the basic V-Ray material and played with the refraction glossiness and the translucency effects. It really gives you a lot of control and since it was for a still image there wasn't much concern about rendering times, which were actually pretty good. After some testing I got to this configuration (Fig.24).


For the gills I applied the same logic. The main render was done in OpenEXR 32 bit and with lots of elements and the necessary multi mattes (Fig.25).



After this render I did two more passes with no lights: one with the mask texture and another with the subdermal layer inside a V-Ray light material (Fig.26).