the box stores offer some OK stuff, but buy more than their estimates, which means two kits for a 425 sq ft floor.....their estimates are quite optimistic, and this in it's self is a major issue with using them (picture almost 3/4 done and you see that you do not have enough material to complete, nor do you have time to "freeze" things and go back to the store)
the double cost of box store product will usually put you in the products offered by vendors who very frequently post here, and provide help to do their floors. Any of these are much better than the box store.
make sure the floor is clean, degreased and in very good shape. You may need to etch or grind to get this done.
Get a helper and two pair of spiked shoes and completely empty the garage.
My attached garage was done with a Rustoleum kit by the builder, it is only 16x20, but the single kit barely got things covered. It is less than a year old and is not holding up well at all. The house next door, same builder and same product, less than three months old and it is peeling in strips.
Cheapest or closest vendor is not the way to go on this type of project. Just not worth it, and the only way to remove a failed attempt is pretty painful and costly.
Do it right the first time....get with one of the folks here, because if you are lucky, Lowes/HD will only send you to the maker.
