tone and tape
Tonal charcoal drawings - no line.
The drawing area was edged with masking tape.
Tones from black to white were noted and shadows drawn in - the white paper itself making the highlights.
Equal attention was paid to the figure and its background. Both need to be observed / recorded if the drawing is going to seem 3D ie allude to form on a 2D surface.
At the end of the session the tape was carefully peeled off giving the tonal work a much more defined finish
Handy hint - if using this method, take some of the tackiness from the tape first. Putting it on fabric and quickly pulling it off will do this