Hello, Rodney,
The epoxy floor I used was manufactured locally, used for power plants and other industrial applications, but it should be similar to those available in the U.S. The new floor needed a topcoat because of problems we had with the first application. Usually, a top coat shouldn't be necessary. The epoxy floor we laid in my old workshop was a single application and also quite glossy, if not as white. We had no grip agent added, but the floor is not especially slippery. Tires don't leave marks.
As you might have noted, we used grey in the separate two-car garage, for the daily drivers. The difference in overall brightness is remarkable, so white wins there over grey. White is not more difficult to keep clean than grey, I noticed. Sometimes white looks cleaner, in fact.
The problem with epoxy is that it will yellow with sunlight. That is why on boats, the general recommendation is polyurethane for the deck rather than epoxy.
Since you are still constructing, read Jack Olsen's 12-gauge garage thread again. He makes a very good case for ceramic tiles. They are easier to install, won't fade or yellow, take wear well, and, if you chip a tile, you can replace just the tile. Lamborghini, BMW, and others specify tiles for their dealer repair areas. There is also a good discussion on tile vs epoxy in the floor section. If I had to do the floor all over again, I would probably go with tile.
You're in the fun part. Enjoy, and keep us posted. Do you have a thread? It will be great to see one from Trinidad. Good luck.
Andy