Use a masonry paint on stucco. Stucco is a combination of powdered limestone or cement, blended with sand and water until it reaches a mortar-like consistency. Applied by hand over metal wire or lath, stucco cures to a hard and durable masonry surface, which can last for years on a homeâs exterior.. Apply a coat of exterior masonry primer to the stucco. Start by brushing the primer around the edges first and then roll on the primer with a thick-nap roller on the flat wall expanses.