To suitably paint a masonry basement wall, if it is unfinished masonry, it will take a technique that is different from painting a finished wall.
Patching – To avoid cleaning your wall twice, patch any cracks or defects before you clean it.
Cleaning - Before applying sealer or paint, wash the wall to remove loosened concrete, dust, or debris.
Sealing – If it is an exterior wall, you'll need to apply a sealing coat to prevent moisture intrusion.
Applying Primer and Paint – To apply primer and paint, choose a paint roller with the right size nap. Refer to the paint manufacturer’s recommendations.