I did a wash of left over color from another painting prior to this days work. Sometimes it can be good when color from the underpainting shows through.
Once the wash dries, I made a 4 x 4 grid in pencil on the canvas an a matching grid on the much smaller photo that I am working from. This lets me transfer the geometry in a more accurate way.
In this case, I used a hard charcoal pencil to sketch in the geometry and then used a mixture of dark blue, brown and iron oxide to create a tonal study.