Hi Robert, you are already using the least inexpensive method with "Seal-able" Rust Prevention Bags. A one time coat of a thin film of a non-oxidizing oil (mineral oil, 3-in-1 oil (mineral oil), Starrett precision tool oil (mineral oil) , or Norton’s special honing fluid (mineral oil)) is an excellent rust inhibitor. Used together, this is all you need to protect your firearms.

I use Renaissance wax on my stainless guns. I've owned a couple Colt snake guns over the years and everyone recommended it to keep them shiny and protected. I spend the winter on the Gulf side, and have been using it (and Flitz) on my stainless guns. Both are good, but check them regularly!

I lived in Virginia beach and use BIRCHWOOD CASEY - RIG® UNIVERSAL GUN GREASE I have a old rag that has been used with rig forever I keep the rag in a ziplock bag and wipe down the guns with it once a year I apply a new thin coat Long-known and highly respected by shooters, this clean, viscous grease is easy to apply to your pet gun and provides absolute rust prevention during long-term storage. One thorough application of a thin film will protect your rifle, handgun, shotgun, or muzzleloader from rust and corrosion
brownells.com/gun-cleaning-chemicals/oils-lubricants/rust-prevention/rig-universal-gun-grease-prod31842.aspx