I got a tip for you about free handing panel lines, if you don't have some of those neat saws like WM, go to the crafts store and get yourself some of that label maker tape. You know the kind that comes is different colors and makes letters with the little gun that punches the tape.
Just get some of that, it's really thick and works as a perfect guide for a reqular scribing tool, it's really sticky but doesn't leave any sticky residue.