I have a GP PT 19 giant scale. There are some scuff marks and such on the wing. I bought some GP lustercote cub yellow paint, taped everything up and sprayed the wing. two coats and still the marks are visible. Should I have reprimed the entire wing before repainting? I wasn't aware that the Cub yellow was considered a "candy" type color paint and yes I shook the paint can aggressively for at least two minutes.