One method that I found not only by accident, but also extremely effective.
Hair!
This happened after a spray job, in which I beleive my dogs hair got onto the model.
I didnt recall a panel line being there, and all others were recessed, so I scratched it for a bit, and it came off.
It really did look like a raised panel line.
To make them, get some hair that suits, wife, yours, kids, family pet (only if you own small dogs, large ones get cranky!!
)
Apply hair to model, and fix in place with a fast flowing CA glue.
Voila!
You can even use the hair from paint brushes, nylon ones preferrably, the cheap and nasty type kids use at kindy.
Hope it helps!