When I first had this problem last year I read that thread and was discouraged which led to the percarbonate experiment, which, in hindsight, was a terrible idea. Hydrogen peroxide "eats", "burns" and/or "dissolves" organic materials, why wouldn't it destroy my shoes... I should have known better.
Man of Lint did seem to cover his bases with "normally" accessible household cleaning products for an entirely different purpose, attacking a smell, which is a far more difficult task. I was wondering if he had purchased a plastic last, lasted the shoe, removed the sole, cork and shank, and then bleached if he would have been happier with the results.
I also have a habit of wondering if I can do something myself "cheaper", hence, I started mixing my own Oxyclean with bulk purchased chemicals which eventually led me to doing my laundry differently.
I am still eying that sample bottle of 2-Phenylphenol, I feel that an aqueous solution has the best chance of saturating the leather of the shoe, but haven't looked up the MSDS to find out how to properly handle it yet. It can wait. Mid-terms begin Monday, delayed from an already delayed schedule. More time to work on my proofs.
As for the "air-tightedness", you can't fumigate an open or drafty space. You can get a large enough box that you can exhaust all the oxygen in the box and potentially put out the candle. That would not necessarily be a bad thing, but means I'd have to watch my accelerant/sulphur mixture so that the sulphur burns but the accelerant doesn't drink all the air.
Also, and worth considering, is that SO2 is a bleach. It makes Panama hats white, not yellow. I may have to re-dye the shoes if the dye reacts. Don't have a problem with that, actually, I'm a bit excited by the prospect because I've found many a vintage shoe in great condition in bland colors. I can only imagine how many SF members will either poison themselves or burn down their houses if this safely (for the shoe) bleaches leather.
The big, million dollar question is, "is S02 Heavier or lighter than air?" because that will determine the placement of the shoes relative to the candle. I had been thinking of suspending the shoes above the candle using paracord in a slightly larger than mini-fridge sized box. But if it is heavier, I should change the orientation.