I have white popcorn ceilings (circa 1980). They look dirty and have dust/cat hair etc. clinging to them. The finish just brushes off when I try to sweep or vacuum them clean. Plus, they are now faded into an off white color and there are water spots in various places. (1) How can I clean them? (2) What do I do about the water spots? (3) Can I paint them a fresh white color, or will that cause the texture to fall off? I would like to get rid of the popcorn texture, but I think it is too costly. Any help or suggestions?