One of my favorite subjects to draw or paint are my oversized gourds, cast in dramatic light.
Before painting I create a loose gesture drawing within a structured grid (see earlier post: Sacred Geometry).
A light grid with vine charcoal is then made on the canvas paper and the gourd is redrawn.
A tonal underpainting will be created, over which a color layer will painted at a later date. For now, I mix 50/50 ultramarine blue with ivory black, with subsequent amounts of titanium white for up to seven increasingly lighter values.
I block in the background with the second to lightest value, and the foreground surface closest to the viewer with the lightest value.
The vine charcoal dissolves and rubs out easily during this process. Next, I put in the darkest darks for contrast on the form.
Last step, a combination of blocking in the lightest lights and middle values. Remember, this will set the tone (pun intended) for the color layer to come, after this has dried for several days.
No over blending, no fussy over attention to detail. Keep it simple.