I love it! You have amazing skill, for this being only your second facial portrait!

I never progressed beyond black-and-white drawing myself, because I don't enjoy the practice enough to actually develop skill. But the most valuable piece of advice anyone ever gave me (because I had a terrible time with faces, in particular) was to "draw what you see, not what you THINK you see."

My tendency was to draw noses as nose-shaped, mouths as mouth-shaped, etc., and they never looked right. When I learned to just start drawing in the shadows that defined each shape, rather than the shape itself, my drawings made a marked improvement. Still nowhere close to good, but definitely noticeably better.

No clue if this might help, or how it might translate to painting, but thought I'd pass it along!