Clean the surface:
Sand/scrap out the surface to remove dust, greases, paint, and other impurities.
Repair the cracks and patches by using a filler or wall putty.
Mix cement paint with water in a proper ratio according to the manufacturer’s instructions. Stir the solution properly to get the proper consistency.
Apply 2 coats of paint for the best results. Let the wall dry for 24 hours after the first coating and make sure that the thickness is uniform throughout.