I have learned that unlike car paints, that are rubbed back with 1000grit wet or dry paper and then clearcoated and rubbed down again for a superior finish. Humbrol enamels can't be
rubbed / cut back!
I rubbed back the car paints lovely, them clearcoated with 2 coats of Humbrol SatinCote. On rubbing it back with 1500 grit it just made a complete mess of the surface, lots of lines and scuffs. I gave it a wipe over with Humbrol thinner on a cloth which softened the surface, then redid a third clearcoat. Unfortunately many of the sanding marks are still showing through
So I have learned once you have used Humbrol enamels, accept the surface for what it is, don't even think about cutting it back for a finer finish!