I started out with a blue Col-erase pencil to block in the basic shapes, refining, and adding detail,with a black Col-erase. Honestly, I wasn't as interested in producing a "perfect copy" of Pete's drawing as I was in learning how he laid down the lines that made up his "cute girl". It took quite a few attempts and I have a bag of wadded up paper balls to drop off in the recycle bin this afternoon. Finally, I used a Design Ebony pencil for the cleaned up drawing.
After scanning the drawing, I cleaned it up again in Photoshop, optimizing it so that I could import it into Toon Boom Studio and vectorize it.