That's an interesting question, and I can't say I know any absolutely SURE methods. I always figured my short stature affected my dd's ability to flip - she waited too long, then I think when she tried to turn, she didn't have enough room. She was a really long baby too. I'm pretty sure that footling breech is one of the positions that cannot be safely delivered as breech, so if he's still footling when labor starts, your doctor will insist on a c-section. It's also about a 1-2% chance that this is how your baby will present. So, how to try to turn? Some suggestions from my Bradley coach: shine a light from your vagina, play music there, have your husband talk or sing to the baby from there, anything that might attract the baby's attention and make him want to get closer to the stimulus. You may also want to consider external version (where a doctor or midwife tries to push the baby into position from the outside of your stomach). The real risk here is that rough handling of the amniotic sac may rupture it, forcing you to have a preterm c-section immediately. The best way to prevent THAT is to make sure the person you choose to do the version is well-qualified, and has successfully done it many times.
I wish you luck. I wish with all my heart that I had known my dd was footling breech so I could have made these efforts myself. Do what you can, and even if nothing changes, at least you'll know you did everything you could. Feel free to PM me if you want. Best wishes!
-K.