on DA http://docwario.deviantart.com/art/Self-Portrait-as-Gsphere-358220605

The technique I was trying to employ was additive, but doing it section by section so I'd avoid losing the shapes defined in the sketch. Always starting with the same darkest value underneath, once you've worked the area around you can add the adjacent part in silhouette, with that dark value. Or something something.

Music is improv jam by my old band A New Sound II, titled "Happy Birthday Earth"