I'd sand it with something fairy coarse first, probably 320, then work to 400grit. Work at it until the rust is gone. When it'* gone and sanded fairly smooth prime it well, and let dry according to directions, then sand the primer with 600grit. Then apply the color coat according to the directions. Apply clear coat according to directions, then let dry. Sand with 800 grit up to 1500 or 2000 when paint is dry. Then use rubbing compound according to directions, giving the paint enough time to dry, and buff to a shine.