Any thoughts on using canned air to exclude air from developer bottles? Since the canister warns against using near ignition sources I assume the stuff is flammable, perhaps propane, butane? Would be necessary to keep canister more or less upright and release the gas through the furnished wand gently, to avoid splashing, etc. Since I have this stuff around for dusting off negs prior to scanning or enlarging it would be really handy.
Do you mean canned air in general, or the "dust off" stuff? I would avoid the latter. Look into a product called Bloxygen. It's nonflammable and inert (argon). Displacement is still my number one method, however.