I would just band it if I were you. Braids can get brittle and break hairs. Norman's mane is like a Friesian's so I keep it banded in the summer to let air in and keep the mane somewhat tidy.
Otherwise you could braid the mane, then wrap the braids in vet wrap and keep it in for a couple weeks. Some people swear by that method. I tried it on Norman once, and it worked pretty well until he rubbed them out. Plus vet wrap can get expensive when you use so much of it.