This was years ago, but I think he used Ultrabrite.
As I said though, I would go to an auto parts store and buy window glass polish. You can use it with a buffer to clear up the glass.
Hi ISUzj. I work for Home Depot in the Chicago area and have a couple of thoughts on cleaning up old glass blocks
Rubbing compound is quite abrasive. Its purpose is to remove a layer of oxidized paint so that the underlying color becomes visible.
I would use a much finer grit polish...
