Instead of starting with a pencil, I jumped straight in with the brush, massing the big shapes and cutting foreground over background and then background over foreground.
Corrections and refinements were easy with an opaque paint. Note that the plane of the scapula in both sketches was placed as a single stroke.
I used just four colors: titanium white, ivory black, raw sienna, and raw umber. That was all I really needed for such a subject under such conditions.
It is a good super-basic palette for exploring simple relationships of light and dark, warm and cool.
Here's what I used:
Jack Richeson / Shiva casein colors
Moleskine watercolor notebook
Winsor and Newton Series 7 round watercolor brush
I'm using a watercolor palette for a mixing surface, but I didn't use any of the watercolors for this sketch.