At L71 you are going to have a pretty hard time taking advantage of it. You are going to contribute to your team doing poorly, unless you happen to be a very well geared (from BC) healer you are not going to live long against L78-79.
That being said, here is what you do.
1. Gather 4 more decently geared, experienced PvPers in their late 70s.
2. Queue up as a group
3. Win BGs fast
4. Earn as much as 1/3 of a level in a single BG.
You have to be GOOD to make this work, as 5 of you have to be able to carry the whole BG. It's very doable, though. If you can win 5-6 WSGs an hour, you can get a level each hour or more.
AV is also good, and offers more XP per win, but the game can often be very slow, and even if you queue with 4 other good PvP'ers it is often hard to carry a team to a quick victory each time.