My dd was posterior until I started pushing, and then she turned. Yes it was a really long labour, but it was so worth it in the end especially as she was a vbac. I would definately do that again any day over another c/s. I had no back pain at all.
Most posterior babies do turn in labour, and I have now read of quite a lot of women that have pushed their babies out still in that position. So don't freak out if your bub doesn't turn even after you try the techniques, as they will more than likely turn during labour. Just make sure during contractions you are in leaning forward positions. And pushing may take longer, but you can do it!!
Good Luck!!