By using BPR and having the WaxPreview enabled, the material had a bit of a sub surface scattering, so now was a good time to use the final model to try out how much the Wax Modifier strength needed to be to get the look I wanted for the skin.
Render Passes to Compose
These are the render passes I used to compose the picture (Fig.15 - 16).
The final image was flipped horizontally because it looked more interesting to me. The forehead marks were painted in Photoshop to make it more interesting, and I also painted some hints to remove things I didn't like and make it more illustrative looking (Fig.17).
I thought it would be cool to show some more steps that are not in the final image, but can be done from the final model and painting. The first is to post the character and create subtle asymmetries to make it more believable. I have rotated the head and made some modifications on the mouth, eyebrows, horns, etc. They are very small, but visible, changes and combined with the pose they help make the image look more natural (Fig.18).
Next I add skin surface details that the original didn't have to the posed model. I thought the original was fine without them, but they are a nice additional feature (Fig.19).
Now is a good idea to use the new surface detail to increase the effect of the skin, which gets a bit lost when some lights and sub surface scattering are used. I will add it in the color. The way to do this is by masking the skin detail by cavity, inverting the mask selection and painting the cavities on the polypaint softly with a darker or more saturated color. Then I render and check how much is enough to crank it so it suits what I want.
Here is a shot of the cavity that would be inverted to paint and a simple BPR render with the pose, now that I have the surface sculpted detail and new cavity detail enhanced. All these details and modifications are recorded on a layer to save them and still maintain the original image (Fig.20 - 21).
Thanks a lot to everyone!