To Glass Alias - There's really no easy way to know what the actual pressure is at the torch since there are two valves (1 at the y connector and the other on the torch) between the regulator and the torch face. I'm guessing it's around 10-15 psi. What is important though is that the pressure is set such that it's no too high that it blows out the flame or requires so much propane and oxy that you end up with really long candles. The startup sequence I show is to establish the typical small torch flame with 3/8" candles - but there are other things that you can do with compressed air - like create larger bushy flames that you would use for 104 tubing
Check out this video link to see the Thüringen torch in action:
http://www.youtube.com/watch?v=sCq-xhwICF8
To fsankar - The air cools the flame as shawnette mentioned so I tend to use it for crayon colors if I don't want to encase them or when I'm setting up color for an implosion marble to keep the color from boiling and spoiling the clear - also nice for putting color on tubing or working thin walled tubing to slow down the heat and provide a bit more control. Otherwise I run the torch normally without the air for most everything else in boro.
I had an opportunity to take a class with Shane Fero last summer and saw how he used the crossfires for his work - I think he was using one of the japanese style air pumps to run them. He uses a Carlisle to apply the frit and do the basic shaping of his birds and the uses the crossfire for the details like the beak, eyes, and feet
Just to clarify compressed air is not a replacement for oxygen - So you'll still need an oxygen source. The upside is that while using the compressed air your oxygen use will tend to be somewhat lower.