those living in s.e. Mi. have to deal with high humidity, year-round. Surprisingly, I've experienced no issues with rifles stored in a gun cabinet ( bolts removed & locked away ) with nothing more than wiping metal surfaces with an old t-shirt before putting them in the cabinet, so no oils/acids from skin contact is present on gun's metal surfaces. I might spray a little rem-oil or WD-40 on the rag, but often just wipe them off. Only rust issue I've had is letting a friend handle a Gold Cup, then putting it away, maybe I forgot to wipe it down,or missed a spot, but next time I took it out of the cabinet, there was a rusty thumb print on the slide. I removed the rust, but the metal was already lightly pitted. Bit the bullet & ordered a new slide.. Lesson learned. That was > 20 yrs. ago, & I've been extra careful wiping guns down ever since. I have semi autos & shotguns in locked cabinets, no dehumidifiers used,
but all were /are wiped down after handling...in the same manner. Had my wife sew some large "socks" for rifles, pistols & shotguns.. made from an old soft blanket. These were used to put over weapons when cased for transport..to keep the inside of the cases clean, from powder residue.These socks get thrown in the washer when they start getting dirty.