“the initial burst of flame... that results in complete distension of the balloon envelope” -- if you’ve ever watched a balloon being inflated, this doesn’t really describe the process; it is long, slow and gradual (and usually involves a very big fan)

Inflating hot air balloons is a dual step process. The first stage is as you describe tsuwm; slow and gradual distension with a fan. The second is my definition (bluff!). I quote, from the link:

HOW DO YOU INFLATE THE BALLOON?
Usually a fan is used to blow cold air into the balloon. When about two-thirds full, the burner is used to heat the air. In the absence of a fan, cold air can be "flapped" into the envelope, but this is a difficult task.
...
HOW DOES A HOT AIR BALLOON DIFFER FROM A GAS BALLOON? A Hot air balloon gets its lift from heating the air with propane fuel. A gas balloon gets its lift from lighter than air gases, usually helium or hydrogen.

Click on the link for more..
http://www.haveballoonwilltravel.com/q&a.html