So, using toned paper, I'm able to do a piece that I'm happy with, has a full range of tonal value (without hours of cross-hatching & stippling) using a felt tip marker, a pencil, and a white gel pen.
Heroes Con is up next for me, and I'll be trying to do these types of head/bust single figure pieces live at the convention for $150 (first come, first served..new list every day). I'd like to stick to mice (because I'm comfortable doing them and we will both be happy with the result) but I'd be open to discussing something else if it's in my wheelhouse.
Below are examples of the types of pieces:
(This was a gift to Terry Jones of Monty Python)
Staff wielding Guardmouse
Leaf adorned Guardmouse