I don't usually have bran on hand, but I do like to make hot grain mashes in winter when it is bitter cold out. They love it. I boil water and pour it on regular sweet feed or Bay's senior pellet and let it sit a minute. Might also be something Rusty would like using his pellets.
Yes, most horses do love that and I think it makes them feel good. Bran is sort of a laxative so it doesn't hurt to have a little on hand. My mares get that after they foal.