do not use any expoxy you can get at HomeDepot or Lowes. that stuff is pretty low-rent. use a commercial 100% solids (nothing evaporates away). i used www.epoxy-coat.com
in my garage build last year and have zero regrets. you really should do it before you move anything in there to garantee good coverage and time to cure. once you put a single thing in that building you will never want to drag it all out to do the floors.
the other thing to keep in mind is temperature. the vendor i used had temp ranges where curing was ok. make sure you're still in that range.
beautiful build you have here, i'd hate to see it blemished with second rate flooring