Remove any outlet covers or lighting fixtures (if possible). Then scrutinize the walls for any defects. Simply fill them in with caulk or spackling compound if you encounter cracks, dents, or holes in your walls and trims. There are also tips and tricks for filling nail holes. Once done with the repair, smoothen the wall down with sandpaper and then wipe it with a damp sponge.
Your contractor will sweep or scrub the concrete first with a dry brush, and then clean it thoroughly with trisodium phosphate (TSP) and warm water, then let it dry. TSP is a mostly alkaline solution that does a great job cleaning grease and oil off concrete surfaces. Brush painting concrete siding costs $138 per 100 sq. ft., roll painting costs $50 per 100 sq. ft., and spray painting $32 per 100 sq. ft.
In addition, paint features such as mold and mildew resistance are important cost factors. Many mold-inhibiting bathroom paints, for instance, cost substantially more than ordinary latex-acrylic paint—sometimes close to twice the cost. Also, paints that come with warranties from the manufacturer may be more expensive depending on the length of the warranty. (A two-year warranty is standard.)