Step #1: cleaning walls before painting

Clean walls are key in preparing a room for painting. Most walls can be washed using a sponge and warm water. For surfaces that have exposure to oil or grime, like kitchen walls, wash with a solution of water and grease-cutting detergent and follow up with clean water to remove any residual cleaning agent. Finish by wiping the walls with a damp cloth.
The most important part of the process is to make sure you let everything dry thoroughly. Applying primer or paint to walls that are still damp can cause a host of issues, including blistering.

Step #2: removing mildew

No matter which room you’re preparing to paint, make sure youaddress any mildrew first. Never paint over mildew because it will grow through new paint, which will make subsequent cleaning and maintenance even more difficult.
You can clean mildew with a sponge and a solution that is three-to-four parts water to one part bleach. Apply the solution, allow it to set for a few minutes, scrub the affected surface with a soft brush, and rinse the area with clean water. Make sure you wear gloves and goggles and allow time to dry.

Step #3: sand surfaces before painting

Rough spots on walls, whether they have been previously painted or not, need to be sanded before they are painted to ensure the paint goes on smoothly. Use sandpaper or a sanding block to dull any uneven surfaces, wipe away dust with a damp cloth and let dry thoroughly.

Smoothing walls before painting is necessary for surfaces previously painted with a gloss or high-gloss paint. For water-based paint, sand with a fine-grit sandpaper. For oil-based paint, a medium-grit sandpaper should be used.

Step #4: priming walls before painting

Use a primer to get the most out of your paint, especially if your walls are porous or have surface stains that need covering up. Primers disguise imperfections, create a smooth surface for your paint to lock onto, and ensure a uniform finish no matter what you’re painting.

There is a primer for every project and substrate. Benjamin Moore’s Fresh Start® provides excellent hide on nearly any surface, even for projects with a significant color change.