Next step is to rub them carefully down (800grt) give the parts a guide coat, so you know where you've rubbed, and be extra careful near edges. not to rub through to the plastic, wash clean after final rub, dry then degrease, re prime any areas that break through to the bare plastic
Painting should be done in carefully applied single coats, and allowed to dry/flash off between them, Lacquer should be built up in the same way, 3 or 4 even coats should be sufficient..
Thom