How much sanding are going to do? If you're removing rivets, do the panel line
after sanding. Most adequately scribed lines shouldn't dissapear after minor
sanding; clean them with a suede or tooth brush.
The Keeper (of too much crap)
Do you mean pre-scribing? It's often a good idea, particularly where you
expect to have to sand vigorously. If you go slowly, and start to see
evidence that the panel lines in the sanding area are going to fade out,
that might be the best time to deepen the scribe lines.