Be sure to test paint/clearcoat compatibility on a piece if scrap first, though. Sometimes a clear coat incompatible with your paint will cause lifting and wrinkling, which are very, very bad and often result in you having to sand everything, including the decals, off the rocket and start over. Metallic paints especially don't get along well with clearcoats; it often causes the metal to separate from the paint.
Fortunately, none of this has never happened to me, because I always check for compatibility. I have used Rustoleum high gloss clearcoat with good results. :2: