There is a thin bulge along the wall of every one of the rooms in my house, presumably where the drywall was taped and spackled. When the light shines on it, it's very noticeable. In some cases, it's 25 feet long (in a big family room). How do I get rid of it (or hide it) prior to painting? It's been suggested that I cut through the existing paint and re-tape/spackle to smooth it out.