I don't know that there's anything out there that won't wash off. I gave up on plastic feeders due to the squirrel holes. I would patch them and there'd be new holes days later. Metal barrels are best.
I don't use em any more but when I did I wrapped them with thin roof flashing. Did the top too. I had a cheap (free) source for the flashing but was very time consuming plus I had to paint em some. Worked ok then I moved to where feeding wasn't permitted. Now I can use em again but the problem is a bit larger, Bears.
"My two most favorite people are Navy Corpsmen and Marine medivac helicopter pilots" - MEJ 0311 1967.