i do have a position that gets a burp out when just patting her back doesn't do the job. I only hope I can explain it right. Its easy once you know what I mean.

You hold the baby with her back against your body, and you are just holding her with one arm, and your forearm is against her stomach. So your forearm is putting a little pressure on her tummy, and you can either hold her up against your stomach, or sort of rest her on your hip. If the burp doesn't come up right away, you sort of rock back and forth so that your forearm is slowly applying a little more pressure, then releasing, then a little more etc... Hollie always gets her burps up this way (and sometimes a little milk so watch out), and when she was very colicy, this was the only position she wouldn't cry in.

I hope I have explained it well enough for you to give it a go, it is amazing how well it works with Hollie.