The challenge on this panel was simply dimensionality. The man’s pants and sweater were both quite dark, so it was difficult to read where the fabric folds and shadows were. Of course, I could guess a bit, given its placement relative to the whole image, but in any case, I wanted to create interest and motion there. So I introduced that in the underdrawing. See the image to the right.
Thus on the oil level I had three basic shapes to render: the ledge, the pants and the sweater. I rendered the pants in dark gray and reserved black only for the creases and deepest shadow accents. Same with the sweater, two tints of dark green accentuated by dark gray and/or black for the deepest creases/shadows. As it turns out, the buttons on his pants piqued the interest, interrupting an otherwise monovalumatic field of grey (hey, I just created a word!). BTW: those buttons were created by removing paint so as to expose the substrate rather than adding white back in on top (which I avoid whenever possible). It’s one of my pet-painting-peeves.