Check out West marine or other stores that have quality marine paints and varnishes. A Few make some very good one part expo varnishes, great UV protection and durability.
I need to look how old these threads are before I post.
System3’s polyurethane is very pricey, but its durability and easy of application blows away any other product I have used. I used some( matte finish) on some high traffic steps ( pau ferro), and it is still in excellent condition 4 years later.
Using Epoxy, I’ve given up on achieving a super high gloss like polished Polyester resin. I wetsand to 2000, then smear a very small amount of epoxy resin over entire surface with small portion of a cleaned new car wash sponge, and let that dry glossy, and call it macaroni. 7.5Ml is more than enough for one side of a 9’6" cedar HWS. It is not perfect but it is not cloudy like epoxy is wetsanded to 2000 and polished.
Historically we were doing polyester resin gloss coats over epoxy since early 80’s or late 70’s. This didn’t work on top of all epoxies but Greg Loehr developed an epoxy that would accept polyester resin coats albeit we were also leaving the sand coat rough (like 60 grit) so the epoxy had a lot of “tooth” to latch on to the epoxy.
Technically this is what is termed a “mechanical bond” not a chemical one… and although it worked, it wasn’t uncommon for the gloss coat to chip after awhile in use as the board expanded & contracted thru normal exposure & use.
Some epoxies would not work at all, even reacting in some strange manner preventing the catalyzed polyester resin coat to even kick off or cure.
Eventually more user friendly epoxy resins were developed. Fiberglass Hawaii offers an “Aluzine” epoxy which was forlulated to accept polyester resin top coats not unlike Loehr’s Resin Research, which I used extensively while building sailboards (and surfboards) in the 1980’s.