They been using this trick for long time. So I have been told-- by few old timers! Get few pair of clean old white cotton sport socks and place three charcoals inside and place it inside the safe. Nothing works better. They knew the importance of the firearms back then, and if was good/ worked for them should also work better now ...I have used a golden rod for about 20 years and it has never let me down. Biggest problem to me is that some safes are very thick to drill and come undrilled. Also, you do compromise the fire rating to a degree, not to mention if the room is flooded. No easy answer.
Not for long storage. I go with RIG. BUT-- The Marvel is my choice in shooting completion with 1911s or ARs. I like it, does clean well the carbon and fouling after you done and keeps 1911 slide very slick, may shave .010~seconds off your time.. We used a 50-50 mixture of marvel mystery oil, and air tool oil for storage of the engines.