One other question: What is the best way to apply grout sealer to a vertical surface, like shower walls? I have tried foam brushes, bristle brushes, small artist's paint brushes, and they are all a pain in the neck. The sealer ends up running all over the tile farther below on the wall, etc.
If anyone wants to make a million bucks, manufacture a sealer dispenser similar to a rotary cutter that quilters use -- imagine a pizza cutter, but the cutter part would have a foam band going all the way around, and the handle would be hollow which you'd fill with sealer and it would dispense the sealer onto the foam strip around the wheel. Imagine running a pizza cutter up and down the grout lines, and you get the idea. It's the same principle as a circular saw blade. Just a thought.