I have a cinder block wall around my back that is a reddish terra cotta color. The bottom three rows were painted a matching color to hide staining from mildew. I was told that comes from the house behind me being a higher elevation. There are a few places where it looks like salts are penetrating, and some random mildew, and I was thinking about painting the entire wall in a light color. What is the best way to prep the wall, and what paint should be used? I'm wondering if a good coating a Kilz is in order, or maybe a sealer of some sort. I would appreciate some tips on such a project.