Thanks! Yeah the grey paper solves a lot of the mid-tone issues. They are the hardest parts of rendering when you start with a white paper so you can cut out a lot of hassle by starting with a mid-tone grey and just focus on black & white. It'll help improve your skills which you'll be able to bring back to white paper.
"Tortillion" is just a fancy French way of saying 'smudgy thing' which is a good descriptive term for a paper stump!