I put motor oil on with a tooth brush and then cover with a sheet [to reduce air flow] on large mass cast iron objects; lathe, mill, table saw, jointer, band saw, and maybe a drill press.
The vapor pressure of motor is high, and I have to replace it every couple months in the wet winter around here, or I wind up sanding off rust. I don't sand off rust on ground surfaces like the mill table. I have to keep them heated and oiled.
Tools in a room a couple degrees above outside ambient may be ok with out protestant for 50 years if the tools are low mass.
The problem is rising temperatures at 100% humidity makes the outside of the large machine condense water like an ice water drinking glass. The big machines take too long to warm up, and are colder than the moist air.
For guns indoors in this climate, they never rust unless they get wet or are touching concrete.
I got a case of BreakFree CLP before the ~2002 formula change, and I put that on guns while cleaning them after I buy the guns.
I had 3 rifles, I was breaking in for hunting in the desert in October, get hit with a sand storm when they were on the ground on bipods.
I am now looking for some dry lubricants.
This forum has a lot of info and some really smart posts
http://www.bobistheoilguy.com/
But the gun sub forum does not have the kind of talent that the other parts of the forum throw at motor oil for vehicles.
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=postlist&Board=38&page=1
Saying, "Tell me about lubricants and corrosion protection." is about like saying, "Tell my about gunsmithing."
The info just goes deeper and deeper.
I am now having a problem with mold spots on gun stocks, especially old military Walnut and old plastic on FALs.