Dip the clean rags into the bucket of water and start cleaning the wall. Over time, the chalkboard paint will get dirty because of general use. All this dust must be completely cleaned off before painting on it.
Let the wall dry overnight. It needs to be completely dry before you begin painting, especially if you are using water-based materials. Otherwise you may have to repeat the whole painting process.
Paint primer over the chalkboard paint. The paint is smooth so you don't need to sand. Once primed, it feels and looks like a fresh new wall. Use the rollers to prime the walls. Once this dries, paint the wall however you want.