Ron you're supposed to clean then seal in most situations. I think mikey was talking about a different application for sealing before hand.
I prefer to use a pump sprayer to seal grout. Although nothing seems long enough to stand upright and seal with that i know of.
I have also found that it's best to use a solvent based grout sealer. Water based has too much of a chance for effloresence.
If you use solvent based a blue grout wand wont last worth a beans.
As far as cleaning it's quite simple. However it is more time consuming to do it properly. You need, a blue grout brush, alkaline, and acid cleaners. A turbo and that's about it that I can think of off hand. You vacuum, precondition with alkaline cleaner (prefered first step). Scrub and rinse. If that doesn't get satisfactory results then acid etch grout as long as you have no reaction or fizing when testing acid to the tile surface. Scrub again and rinse.
You can have problems with poorly installed floors and you can test by trying to find hollow spots by tapping on the tiles, and warn customers of potential problems.
Learning to color seal is a great opportunity for extra income also.
