Use Kilz primers after removing mold and mildew using a solution of bleach and water or a mold-killing cleaner and allowing the surface to dry. Painting over mold or mildew without removing it is a temporary measure at best, according to the primer manufacturer.
Some Kilz primers include a mold-resistant ingredient. By combining the mold-resistant primer with a similar top coat after removing mold from the surface, the painter reduces the chance of the return of mold or mildew to spoil the project. When applied after cleaning mold from the surface, the primer prevents any leftover stains from bleeding through the fresh topcoat.