I’ve started playing with using a dark sienna conté crayon to block in areas of shadow on the toned pastel paper. The highlighted one here is on soft gray paper. I like it because it is good example of the less-is-more principle.  However, I’ve also found that warm dark shadows also work on the sienna toned paper. Then, the hue contrast between figure and ground is less strong, allowing the figure to gently emerge from the paper.

Here are two fifteen minute studies, one above and one below. Conté pencil highlighted with conté crayon on toned pastel paper.32.5 x 50 cm or 13 x 19 3/4 in.

A few four minute studies.35 x 50 cm. or 13 3/4 x 19 3/4 in.