Richard
I applied panel lines on my Ziroli Zero on the top of the wing and fuse only. After I completed sanding the primer smooth I used 3M Fineline tape 1/16" for the panel lines. I measured and scaled up their location from one of the many books available. After I applied the tape I then applied another coat of primer over the entire plane. Then sand the primer until the tape has no primer on it. Then, this is the fun part, remove all of the tape and lightly sand any feathers that might appear. Once this is done you are ready for paint and the recessed panel lines will show up nicely. One more thing to remember is that there is no tape to come off in flight. Good Luck
Fred