Do you know where to buy some modest quantities of dessicant? I like the idea of burying some stashes. I live in the desert but underground there can still be a condensation problem.
Silica gel available in small packets.
OR
DampRid which is available at most hardware stores, drug stores and many other outlets.
Search on Google for "dessicant packs" (without quotes) and you will see lots of places selling them, like this one.
Try a Hobby/Craft store. Ask for the stuff used to dry flowers. They’ll now what your talking about. I got mine in 5 pound bulk boxes for about $12.00 each. You can then divide up into small homemade packages, preferably of a tight woven burlap or heavy cotton.
One of the best rust inhibitors is plain old vaseline. Google vaseline rust prevention. Any brand of petroleum jelly. Dessicant packs can be made by putting a scoop of the gel type of kitty litter in a sock. Same stuff.
Almost all gun shows have vendors who sell ammo boxes, accessories and desiccant (one “s” two “c’s”) bags of various sizes. Desiccants are chemicals that remove moisture.