I don't feel like the glue/epoxy used is critical. Worst case scenario the knot falls out at some stage in which case you simply glue it back in. If anything, using a less "secure" product will just help the next time the brush needs to be reknotted.Thanks everyone.
I was concerned because I didn't have "marine-grade" epoxy & I didn't know how much to use.. I ended up using Gorilla Glue epoxy. I like Gorilla Glue products...always had good luck with them.