>> Cinder block can be painted.
It may take less paint and give a better finish if you rub off some of the rough spots first. If you have some chunks of broken cinder block, those are easier to use for "polishing" the surface than a whole, heavy cinder block. It might go easier wet, I'm not sure. We did the "polishing" on an indoor wall and couldn't easily hose it down.
I was just talking about the use of stone tools by Homo Whatever 2.5 million years ago, on another website - but this is a really NEO Neolithic application. High-tech rocks.
