Hey skyhawk;
I assume you are talking about a wing that's glassed, sanded and ready for a paint job. Get yourself a roll of fine chart tape (graph tape) with about 0.5mm width. After transferring the scale layout of the panel lines onto the wing (top and bottom) with a pencil apply the tape. Now you are ready for a couple of coats of white automotive primer. After the primer has tried apply a third coat just over the tape lines. Let it try over night and pull the tape the next day. You can slightly sand the entire wing carefully with minimum 400m, better 600 wet & dry. Don't sand too much. Now you can either go ahead with an elaborate rivet job or finish your paint job by applying the top coat. The lines will show up very nicely, even after two or three final coats. Hope that helped you. There are other methods, but I found this one very easy to accomplish and the result is stunning.