The Continuing Struggle With Skin Tones

We never really learned about painting skin tones in art school. I'm wondering why. We had SO much drawing and anatomy, so I feel fairly confident about my drawing skills, but when it comes to painting faces, I am lost.

Over the ensuing years, I've gone to museums, asked friends for advice, looked at many a painting or tutorial on the Internet, but still— I struggle. This afternoon I worked on The Chair, and made some decent progress on one of the figures on the left. I'll post both today's work and then below it a picture of what it looked like last time so if you are so inclined, you can see the difference.

The Chair, © 2017, work in progress (click on image for larger view) 8/31

The Chair, © 2017, work in progress (click on image for larger view) 8/22

Mostly I seem to be timid about going dark enough in the shadowy areas, so the work I did today was a step forward. But I think I should go darker.

Well— I also worked on Stockton Street this morning:

Stockton Street, © 2017, work in progress (click on image for larger view)