I painted a new garage floor last month. I used a 2-part epoxy concrete floor paint kit which included cleaner and some decorative traction stuff, but I used sand instead. It was $80 per kit, which has 1 gallon of paint and is supposed to cover 250 sq ft. I had 380 sq ft, plus 3-8 inches of concrete block wall, which being rough and porous was thirsty. I used 2 kits and ended up with about a quart left over.
I chose a color and the paint store added pigment at no cost. I thought about white to give it that aircraft hangar look, but ended up going with light gray.
As stated by others, prep is 90%. Clean, clean, clean. You'll need a deck brush or stiff push broom for scrubbing, and a 3' squeegee to remove the rinse water after cleaning. My garage floor has a steep slope (6" in 18') which helped a lot in removing water.
You can mix the sand into the paint or sprinkle it on after. I tried both techniques, both worked. If you mix it in, stir thoroughly and often or it'll settle quickly. If you sprinkle, practice first so you can lay it down uniformly. It doesn't take much.
The floor has to be above 50F for proper epoxy cure. Needless to say the epoxy has a pot life after mixing which depends on ambient temperature, the kit gives the specs on this.
I thought my floor came out great, but maybe this was just a pigment of my imagination ...
