To try the impasto technique used by Rembradt could be a fantastic experience to do (in italian we use the adjective "materico" for that kind of impasto). I used a similar tecniques on some past studies, but this time I wanted to focus myself just on the shades of colors and on the shadows and highlight on the face, just to exercise my hand on the detail of a face (when I work on my own painting, my subject are a very simple face :D ).