Best Answer: You can skim over painted walls as long as the surface is otherwise sound. As a decorator I have it done all the time. When I very uneven walls it is usually quicker and a ten times better looking job than any amount of filling or lining paper.est Answer: You can skim over painted walls as long as the surface is otherwise sound. As a decorator I have it done all the time. When I very uneven walls it is usually quicker and a ten times better looking job than any amount of filling or lining paper.