I use the outdoor/post/fence acrylic paint. Those are really good and cheap. Paint like 3-4 layers and it will last for years. You can use the stuff Jeremy recommended but I think it cost more.
Yeah it's not cheap that's for sure, it's a lot than cheaper than Resin Research though, or the Aluzine Clear from Fiberglass Hawaii, they're $50 for a half gallon
Paint ain't much cheaper than $30 a gallon so I say go for it. I wouldn't worry about sealing it up with epoxy resin, it's not supposed to hold water, even if it will get moist from evaporation/salt creep, btw do you have any way to vent the inside of the canopy? that could go a LONG way to making it last and reducing damage.
Use an outdoor paint, or one for high humidity settings (bathrooms) and you should be fine, pool paint.. well hell I guess if that's under water it'd work as well, although double check that, most pools are not made of wood it might be specially formulated to adhere to concrete only.