Second, what is the best paint I can buy for the job.
Surwinn Williams Tile Clad HS. It is a True Epoxy paint. It is used to paint the inside of water towers. It is some of the best paint you can paint your garage floor with. It comes in colors.
We've used it in industrial auto shops. The only thing that will take it off is dropping a brake drum and chipping the concrete.
Now....It's smallest quantity is 1gal. a 1gal Kit is 2gal's. 1gal Part A & 1 gal Pt B.