I actually use a type of hair spray when doing my horses' manes. Its from loreal paris "Tangle Tamer", its like, $3 at the store, it smells good and it doesn't leave his mane gross. Here's a link:
And I also agree with the braiding/banding. That's what I do about a week before a show, leave it in for about 5 days, wash it(if you can) 2 days before, braid it the night of, and put a sleezy over it so it looks professional.