2) An epoxy primer; this is typically a thin epoxy, and usually a water based epoxy or a thin solvent thinned epoxy. Floor epoxies generally stick well to good cement, but primers tend to soak into the cement a bit and provide even a better bond and thus a lower chance of running into later problems. Most commercial epoxy applicators and commercial epoxy kits use a primer. Many homeowner systems skip the primer and do not do the degree of surface preparation used in commercial environments, which is why many think that having your home done commercially or professionally yields better results. The truth is, the better prep the better the results, regardless of whether or not you use primer. Other primer options include 1 coat of a low v clear epoxy thinned about 15 percent with solvent, or a solvent thinned first coat of our solvent free floor epoxy applied very thin. Primer is a good starting point, and it can also help reduce air bubbles that can come out of the cement and get trapped in the epoxy (however, this is more of an issue if the cement is in direct sunlight, temperatures are rising, and/or the cement is very porous.) Priming or lack of priming is your choice, with good surface prep, and a good epoxy product you do not need it.
3) Epoxy main coat - this is typically done with one (sometimes two, depending on the product) coats of either a solvent free floor epoxy or a coat of a water based floor epoxy. Main coat options including colored chips for color other than gray, anti slip grits, to give the surface a course texture, and promote less slipping, and various other products like this can be added to the main epoxy coat or to a second main epoxy coat (usually a clear epoxy like our Low V epoxy). If chips, sands etc. are used they are often covered with another coat of epoxy to ensure that it all sticks!
4) Polyurethane (clear or colored) is an epoxy product enhancer. It is used on top of the epoxy floor systems because the epoxies will yellow in sunlight, lose their gloss quickly, and can scratch easily. The better the product, the less need for an added top coat, as many offer a poly topcoat, the more basic products don't. However, there are lots of clear coats to choose from. The best choice is a 2 part polyurethane with lots of UV blockers (like our acrylic poly plus), which will keep your epoxies from yellowing.

There are many epoxies and needed added products out there. If this is not an option you want to explore for your garage floor, try a garage mat, or some other garage floor covering.