I've read that P-51's tended to have their wings puttied, sanded, and painted to hide the rivet dimples and help facilitate the "Laminar Flow" design of the wings.
I also understand that the repainting process in the field would often remove the putty and reveal the rivets. Damned if you do, damned if you don't.
But....it's YOUR model. Whichever way you jump....ENJOY!!!