I heard Jim Lee (THE top comic artist of the last 20 years) speak long ago about non-photocopy blue pencils. You sketch in pencil, then pick out the best lines in non-photo blue and erase, only the blue lines will remain, allowing you to have a nice wire frame for your drawing that can easily be removed upon scanning. These days, you can even do it with a mechanical pencil: Like this Pentel Sharp 205 with 0.5mm non-photo blue lead.