Charcoal is just one of the mediums that is doomed to be messy. I like working with vine charcoal most but it requires special paper or it seems to just rub away too easily but I never could afford paper with a heavy tooth to it.

I've always sharped with box cutters. I have one for charcoal and pastels and one for colored pencils. I'm especially meticulous when sharpening my colored pencils. they're just so expensive. To avoid cuts you just have to be careful and always remember to cut away from you.