Sweep dirt off the surface of the cinder blocks with a wire brush.
Spray the blocks with a pressure washer or hose to loosen and rinse away any remaining dirt. Allow the blocks to dry in the sun.
Use a paint roller to paint the blocks with exterior latex masonry primer, often called acrylic block filler. Press on the roller to squeeze the primer into the small holes in the concrete. Let the primer dry for six to 12 hours.
Apply two thick coats of 100-percent acrylic latex house paint, allowing the blocks to dry for six hours between the first and second coats. Use a fresh paint roller and plenty of pressure to fill the holes.
Allow the blocks to dry overnight before moving or touching them.