Brush the wall free of debris and dirt with a broom.
Fill a bucket with a masonry paint stripping agent and brush it evenly onto the block wall.
Wait for the stripping agent to break apart the paint on the block wall as instructed on the packaging of the paint stripper.
Cover surrounding plants with drop cloths to protect them.
Fit the power washer with a 40-degree fanned tip and hold the wand of the washer 7 inches away from the wall. Spray down the entire wall with long, sweeping movements to remove the paint. It is best to protect your eyes with a pair of goggles during this process.
Wait 24 hours for the wall to dry thoroughly.
Pour a masonry primer into a paint tray and roll it evenly onto the wall with a paint roller. Once the primer has dried completely, fill the tray with masonry paint and roll on an even coating.
Fill a garden sprayer with a masonry sealant and spray it evenly onto the block wall in a single coat once the paint has dried.