Thank you those links and suggestions. The subtones idea seems particularly promising. Even some respected artists darken skins with the diffuse node and that always looks like paint to me.

For me, the best dark skin out there belongs to G2 Kelvin.

Poser 11 Pro, Windows 10

Auxiliary Apps: Blender 2.79, Vue Complete 2016, Genetica 4 Pro, Gliftex 11 Pro, CorelDraw Suite X6, Comic Life 2, Project Dogwaffle Howler 8, Stitch Witch