Whats the best way to clean porcieln tile floors? And granite tops.?

As far as granite counter tops they are usually covered with a treated protective seal so a sponge dipped in water and mild detergent, and gently use a plastic scrub pad to remove stubborn surface dirt. If its a spot where there is a lot of soap scum or build up then you could use 1/2 cup of ammonia and 1 gallon of water. With the porceline... the ONLY thing that has worked consistent for me are the Mr. Clean MAGIC ERASERS it may sound crazy but those lil sponges work miricales with my porceline sinks, tubs, and floors. See how this helps!

Your problem you're facing is to somehow get a cleaning solution down between the tiles and into the crevices of the grout, and then get it back out. I like to use a carpet steamer, the kind that looks like a vacuum cleaner. These machines shoot down hot water and detergent with a lot of force, and then suck it back up. That will get all the dirt between the tiles. No hands-and-knees work involved. It should clean your tile floors nicely.

I use glass plus on my granite, works good with streak free shine I would be very careful about what chemical, to use on your porcelain, lots of chemicals attack the grout. I would never consider anything acidic for cleaning.