I have 750 sq feet (3 car garage) prepped for %100 epoxy or maybe polyurea. I spent a week cleaning, scrubbing and acid etching. The floor is nice and clean and very porous now. There are several old oil stains that still show but they all absorb water nicely. Some say to start with a water based prime coat because it penetrates the concrete better to create a barrier between old oil stains and whatever %100 solids base coat you decide to use. This would seem to make sense? Others say water based products are inferior and not to use them?