Hi, G. Let's stick with the garage. The Behr 1-part epoxy is a good choice. The rest is even easier. Check the can for recommendations from Behr. And they probably have a web site with an E-mail address or similar or a phone number for a help line. Contact them and see what they suggest. They know more about the product than your friends and have an interest in seeing the job done right too.
Just a suggestion, but you might also ask them about when and how to put sand into the paint for a non-skid surface. My guess is that you would want to spread the sand over the first coat while it is still wet and then apply another coat. Without it, the floor could be real slippery.