Dear Felicity,
Using a blow torch is actually quite simple. It requires (well,
maybe not “requires”, but it is certainly very helpful) the use of
circular breathing… This is a technique familiar to most wind
instrument players. It basically works like this: (quick caveat,
this is much easier to demonstrate than it is to write about!)
-
While keeping your lips together, you puff up your cheeks with
air (kind of as though you were blowing up a ballon). This allows
you to inhale through your nose while maintaining a small amount of
pressure in your mouth… Make sense? Or put another way, puff your
cheeks up and find a way to hold it while continuing to breath
normally through your nose.
-
Next, slowly let the air escape from your mouth (using the mouth
piece from the blow pipe of course). You do not need to let a large
amount of air out!! It only requires a little bit of air from you to
use the blow pipe effectively.
-
As the air in your mouth runs out, periodically puff your cheeks
back up again in between breaths to maintain the pressure.
Okay, so in retrospect, that is not a very good description of the
technique… However, you can rest assured that Kent will show you
how to do it and it won’t be hard to pick up.
As a side note, if you want to be able to practice this in advance,
just get a small coffee straw or one of those other useless, tiny
straws. Stick it in your mouth and treat it like the mouth piece of
the blow pipe.
ABOVE ALL REMEMBER THIS: The use of the blow pipe is not dependent
AT ALL on the use of your diaphragm to physically blow out the air.
It is entirely the pressure that is built up in your mouth from your
cheeks. So, if you find yourself trying to blow air out in the same
manner as you would blow out a candle, you are doing it wrong! 
If this isn’t helpful, please let me know and I will try to come up
with a better way to describe it. Otherwise, have fun with your
class. I took his class in 2000 as well as his terminations class in
2005 and have been doing granulation ever since. It can be highly
additive (though equally tedious) 
Erich C. Shoemaker
Erich Christopher Designs, LLC
www.ErichCDesigns.com