I was trying to integrate a few elements of a slightly different head building drawing method into the one I use most often, at least in my head. Emphasizing the volume of the teeth volume was indeed useful in the first stages. The thirds I used for many years proved themselves to be helpful yet again. The curve from the top of the ear to the corner of the chin helped with the initial shading.
I went from a long analysis to a drawing mostly from memory in graphite, and then to a dichromatic study in acrylics. I also tried using a round brush for acrylics as suggested by fellow artist, who borrowed me a smaller brush, but nothing could replace filberts for me yet.
I have chosen a blue color instead of black just because I dislike mixing tinted grays in acrylics - just looking at it destructs me with its subtle undesired hues.