we had wallpaper on our walls previously, some of started to peel of so it was stuck back on with kids pva glue. We have taken the paper off, sanded, primed and painted the walls, but where the pva was put there are still marks! can anyone tell me the best way to cover the marks up ( without using lining paper) the depth of these marks is the depth of a layer of paint, everytime i sand the marks it just ends up flaking the paint and making it alot worse!!! please advise me on what i can use or do to cover these marks up.