I have used National Chemical Labs Ceramic tile restoration cream many times to great effect. the process used to be two step involving two grades of powder, but this is a one step process. just squeeze the cream into the area with a little water and polish to dry for about a minute (similar to MB-12 but takes less time). Use a weighed floor machine (but weight doesn't need to be severe). Below are some before and after pix.
Baird
