If you paint over dirty, oily surfaces, the paint will easily chip or peel off. So before painting, clean grimy areas with a deglosser or heavy-duty cleaner intended for prepaint cleaning. They work well to clean painted, varnished or enameled surfaces to improve the adhesion of the new paint. They’re ideal for cleaning greasy or oily areas like kitchen and bathroom walls and removing hand marks around light switches and doorknobs.
to be the devils advocate i have been a building contractor 20 of the last 30 yrs. i do know that if you go to a higher sheen of paint and or darker colors then any imperfections in the walls will show up much more dramatically…therefore the painter or a good drywall finisher is needed to prepare the walls extensively. this could cause more expenses…for it takes a lot of time to prep walls (smooth walls..not textured walls) and this cost has to be absorbed.
Thanks, all, for your time & efforts adding to the article & comments, especially Dave urging requesting both General Liability AND Worker Compensation insurance certificates to protect from real & fraudulent liability--from my experience especially in California, where insurance fraud is a popular income thief, even causing car collisions to collect.