The main problem with enamel paints is that they take a long time to fully dry...... I'd say don't do anything with the painted bodies for about 2 weeks. You can use a polishing kit once they fully dry, or, you can glosscoat them, but, enamel glosscoats will eventually yellow over time. Again, give the glosscoats a good 2 week drying time. You can polish out any orange peel but be careful not to rub through on the high points of the body. It really is not necessary to "seal in" decals although it depends on the look you're after.