The difluoroethane in products like "Dust Off", typically used to move dust off film and into the air, is unreactive and will displace air quite nicely. You can even invert the can and spray some liquid into a bottle and cap it as it evaporates to displace even more oxygen (just pointing the nozzle into the top of the bottle and shooting gas in always brings more air with it). Just be sure not to cap it before the bulk of the liquid has evaporated and displaced the oxygen, and never do it with a glass or other rigid bottle.