My conclusion (I'm the OP) is as follows:
1. Liberally pour in co2 (or Argon) through the bunghole like I always have
2. Quick, slam in a stopper that has TWO holes - one of which is pre-plumbed with a second co2 tank that is ALREADY FLOWING ... and continue to overflow co2 out the other hole in the bung stopper
(at this point I probably have 95% co2 in the headspace ... and rising, since I continue to flow through the bung stopper)
3. turn on my pump
4. Insert pump line into second hole of the bung stopper and turn OFF the tank
5. vacuum to 20", turn tank back on and refill back to 0"
(repeat step 5 2-3 more times)
6. clamp both lines, walk away
I'm only going to vacuum to 20" because I don't need to stress the container and I don't need to run the pump an extra X minutes and I am starting with (probably) less than 5% ambient air to begin with ... after two reps of this I'll bet I am 99.5% co2 ... maybe I'll do a third rep for good measure or maybe I'll do the first rep to 25" ... but I don't think I am going to pull it all the way to 30" ....
Thank you very much for these comments and guidance!
