I take it the lines are there, but real faint? I use the backside of a #ll blade to start with, then I'll go over it with a panel scriber ( if you don't have one, you can keep going at it with the #11 blade ). If I need a guide line, I'll use that plastic Dymo label maker tape. Try to practice on an old scrap body first, and I've also noticed that some styrene is harder than others, so watch how much pressure you use.