As I said this is a pretty useless onetime deal thing, but it's good for a little bit of fun.
Basiclly level to the highest level of your bracket and get to the point where you need to hand in one Q to ding. When the option to enter battle comes up hand in your quest then enter battle.
I mean you won't have your new spells etc. But it pretty fun, and alot of people will ask how you did it. I had a 70 shaman in full Glad and some Vindicators in the 60-69 bg.
Enjoy