i've tried a few products with same results. i used astko orange top and blue top and sunbrella 303. used them on car covers and grill covers and mower covers too. it helps with static water for a short amount of time so helps bead it up and allows it run off while it's working. after a while the standing water gets thru it. if you take a hose to it it won't help at all. the 303 fabric guard at least helps with uv protection, so it's worth some thing.
the worst is getting a full thermal wet. takes forever to drip dry and then air dry.