We are adding a new bathroom to my parents' house that will be more accessable for my 80-yr-old mother. I saw in a recent article in TOH about penny round tile that unglazed porcelain tile is good as a non-slip surface. We have been looking at some American Olean unglazed porcelain tiles, but my question is whether this type of tile is harder to keep clean? And, I have read that I will have to put a release agent on the tile before I can grout it or the grout will stick - right?