Shame col-erase doesn't scan well. I pretty much ignored using col-erase for anything but animation in my first two years at uni, but started to notice in other people's work how you can get such a variety of line, instead of swapping between different pencils.
I pretty much avoid the face like the plague. Mostly I run out of time, but if I'm honest, I have little to know idea of how to go about constructing the face. I'm learning, slowly, but need to do alot more work.