The folks at West/Gougeon suggest troweling on a thickened
epoxy using a notched trowel so you have a known and constant amount of material, and then rolling it with a roller to knock it down making it similar to a stucco finish, with non-skid granules in it. I think I'd be more partial to just gluing on
Treadmaster though, because so many non-skid surfaces can really wear a hole in foulies and flesh, and the application is so much simpler, gluing down rubber sheets instead of experimenting with "stuff" that you don't know the final result of, unless you start experimenting on scrap plywood.