Witchheimer- Thank you for the welcome!
As for skin tones- Short answer: Watched a few B&W movies before painting.
Long answer: I think it's a matter of personal taste. If you watch some B&W movies, most skin tones are darker than a white shirt, for example. I tried painting as such, but it just didn't look right on my first miniature. So I went lighter. In truth- it's really hit-and-miss. Though it's less realistic, I prefer a much lighter face- but I have done some darker shades, and they turned out all right as well; and it is more realistic to have varying shades anyway.
Specific colors used (For the lighter skin): Base- Reaper Ash Gray; Midtone- Reaper Granite; Highlight- Reaper Dove Gray. And shift down a value or two for a darker and more realistic B&W face (Caucasian that is. I haven't tried other skin colors yet.)
Hope that answers your question- I hope I wasn't too long-winded!