Cabot products have me sold with a sanding sealer[although shellac might work here too] compatible with spar urethane[glossy,semi gloss,or satin] burnished with 0000 steel wool.Sand between your thin coats and you can get it looking like glass if you want to but beware of putting it on too thick.Use it on my sinewed bows too & even in a light rain or heavy fog it has stayed sealed for me.No way of stopping moisture over the long run though so I don't push it over a full day.
I use watered down TT3 2 times then straight on my silk wraps instead of super glue.Use that on jute or hemp handle wraps too.Takes a finish good afterwards.
Also snake skins get an 1/8" wide thin bead of thin superglue on the edges then sanded before finish.
All of these have proven to me to be very durable over years of use.
