Before you apply that flat clearcoat over the gloss black, be sure to scuff the gloss black so that the clearcoat has something to bite onto. If you don't do that, everytime you hit the cowl, the clearcoat will chip off. Just use a scuff pad which you can purchase at any automotive paint supply store. I scuff down my entire airplane before applying clearcoat. Be sure to remove all the dust and oils by wiping down with something like acrysol before applying your clearcoat.
