You do better to have good ventilation, and deep bedding. My biggest wrecks with frostbite, have not when it has been bitter cold. We tend to be very dry when that cold, but rather, when it has been bitter cold, then we have a big thaw, and a cold snap.
Manure tends to pile up on the floor of the coop and freezes solid. When that thaws, it must really release moisture, and with the following night, that moisture causes frost bite.
This year, I am being religious of sprinkling a little scratch across my bedding once a week or so. My birds will scratch and break up the manure into smaller bits that tend to dry out. They will flip the bedding. That should help with frostbite.
Don't think vaseline, think ventilation and DRY.
Mrs K