Speaking of tailbags, one might come in handy for next time you braid to stop it from turning from a braid to a knot...unless you did use one and just didn't mention it.
My advice for the tail is: Peanut butter. That's right, PB. Get a big, cheap jar of smooth or regular and butter that sucker up! Leave it sit as long as possible but DO NOT turn him out with other horses while its in. Then just work the knot out, rinse throughly, and load with fly-spray (to cover up any leftover PB smell)