Aw, what the heck. I'll post a step-by-step progress.
I usually like to build up tone slowly, but lately I've been trying to take a more alla prima approach and try to get accurate colors in at 100 opacity. So this isn't usually how I work.
(By the way, this was a 40 minute pose, so you have an idea of the time frame.)
Step 1: Try to nail the silhouette. Generally if you do this, everything else will fall into place nicely.
Step 2: Block in the areas where the light hits directly. It'll help to fill in everything later.
Step 3: At varying opacity, add color.
Step 4: Deal with subsurface scattering and bounce light by adding saturated color at low opacity.