True or false, can charcoal go over graphite

True, you can mix medias

I don't mix charcoal and graphite myself because the charcoal is just too soft in comparison for my taste ... Don't put the graphite down first in any area you will want the carbon pencil (or charcoal in your case) because the graphite makes the paper too slick in most cases for the carbon pencil/charcoal to stick to.