Having done various paint/epoxy/etc treatments to home and race shop floors, at all price levels, my 2 cents is - DON'T BOTHER!
Get the snap-lock tiles, there are various brands available, some as little as $2.99 sqft.
Super durable, and better, you take them when you move.
Few pieces of tile advice:
1) don't get anything with "texture" (like the treadplate style), they are murder on the knees when you're working, and make rolling/sliding stuff around the garage a b*tch.
2) think about the smallest pieces you work with in the garage (small bolts and washers), and buy your tile "open area" size accordingly.