Draw Heads, Draw Heads, Draw Heads.
As a figure artist you really can’t draw enough heads, from every view, every expression, every age, you get the idea. Digital painting sketches done using Photoshop, totally from imagination and knowledge, and a lot of practice drawing heads, no reference of any sort used at all.
The Illustration painting sketch on the right was altered to create the one on the left.
Above; Digital painting showing head rotated away from viewer based on original painted image on the right.