I have tried auto grade finishes and beyond.... they don't hold up. I tried that Nyalic stuff... developed for space capsules and used on the bottoms of aluminum boats... it doesn't hold up too well. Aliphatic Urethane... doesn't hold up. Try and try.... epoxy seems to be the best but it is a pain in the @$$. Do what I do... train your girlfriend to help with the epoxy
. Or pass them off on Fishaholic as I sometimes do
-Dave