Finally, a thread I can sink my teeth into. I've been painting now for 35 years, have owned my own business since '98, and I'm one of 6 Moderators on the world's largest professional painting forums, Painttalk.com My name their is the same here, so it's easy to confirm, just fyi.
Although there are a few products available at big box stores which aren't half bad, epoxy isn't one of them. The quality of resins & pigments are among the primary reasons, but there are others. HD uses rheology modifiers in some of their Behr paints to make it "feel thicker", which seems to appeal to the DIY'er, but you'd likely here most pros complain that it just causes drag and impedes flow & leveling. Another key point is that if, (God forbid), you have a product failure from using a big box store product, you're pretty much on your own, whereas having solid relationships with local paint stores means that they'll stand behind their products.
Most of the products I get from big box stores are primers, (BIN, Zinsser, Kilz, etc). The only exception is ReadySeal, which is my #1 favorite oil-based semi-trans stain, and can be found at some HD's & Lowes.
Sherwin Williams has some excellent commercial/industrial-grade epoxies that are infinitely better than HD or Lowes, as does Benjamin Moore, (especially their Corotech line).
