In this stage I defined the direction of the light and the placing of the light source. The main source comes from the top left. More subtle sources of light especially for teeth have opposite side. I continued with laying shadows and lights.
The techniques which I used are learned by myself by copying photos. I did it when I started my adventure with digital painting. I don't copy photos any more. The technique can be used for photorealistic portraits and for everything. Thanks to this technique I've found my own way of digital painting. I created natural and emotional portraits but not photorealistic. For me they are not very satisfactory. I enjoy working with it.
The key is just using two types of brushes. First the most known simple round. And second my favorite.
Every kind of distributed brushes will be good. It's just an example. First line shows just one press.
Second line shows many presses with many sizes. Third one shows longer press which creates a line. The key is to use the brushes just as short press. The example is based on black 100% opacity and 100% flow.