This wall is in a garage. A small shelf was removed from the wall, which accounts fro the two large, fill areas (black arrows) and the collected dirt on the wall. Even this much area could be touch-up painted, but since the rest of the wall is in such bad shape, it will require a complete painting. Something this home owner should seriously consider is to first paint with a paint specifically designed to cover any and all stains. Most regular, flat white latex interior paint will NOT accomplish this in a single coat. If you do not properly cover many stains, they will bleed through the covering paint and be visible. This can happen very quickly in some cases. Talk to your paint store owner or hardware man for help in selecting one of the paints that does cover in one application. After putting down that 'covering coat,' then go over it with your final white (or any other color) coat. When you're painting an entire room or wall, be sure to remove all electrical covers, such as the light switch plate cover shown here, and wash/clean them with an appropriate cleaning solution.