Ya know... I probably wouldn't try burning the O2 off as in my OP. I was just mentioning it to offer ideas to a member asking for them. I think if done properly, it would be safe, effective, and WAY TO COMPLICATED for the benefits.
There is benefit to purging the secondary for any beer that will be aged for an extended time. A quick read of any of the brewing books or this sight will describe the nasty stuff O2 does to beer.
IMO, the blow off tube idea would work so long as you don't have any overflow. I think I'd try my 2nd stated idea(which interestingly enough, nobody commented on):
Pitch a 'starter" of yeast, (wort or dextrose), and boiled/cooled water and wait 24-48 hrs.
Maybe I'll do the math and see if it seems feasible. Anybody else, please feel free to chime in!