If the covering is plastic (MonoKote or similar), you'll need to clearcoat the panel lines, or they'll smear and rub off from handling. You can use Top Flite LustreCote, but just mist the first couple of coats. If you apply it too heavily, the panel lines will run. If you use Flat clear, it will dull the gloss of the cover, which IMO looks better on a warbird, or you can use the gloss clearcoat .