Mark,
Have you ever ran into problems introducing moisture into the metal containers of wax?
I have. It was years ago when using one of the original formulas...yellow tins...of M26, then switching to another wax at the time and not opening the can of M26 for awhile. Actually, didn't re-open that can of M26 for probably a couple of years.
The reason I didn't re-open that can was because at that time, mid-80's, I found M26 to be a pain to remove (though it was user error...applying to thick and didn't know any better...yet still found other things to remove easier).
When I did re-open that tin of M26 the entire inside of the can was full of rust, so naturally I wouldn't use it and I threw it away. Haven't bought a tin of M26 since, though I'm not apposed to the idea of buying a new tin of that wax.
Dampening the applicator is/was a pretty common technique back then, and some companies may still endorse that. I don't know. I'm not saying it's wrong, but I can think of numerous ways of introducing heat to wax to make an applicator easier to load.
Of course, then again, it pays to open and check your products from time to time.
I can't even guesstimate how many cans of so many different paste waxes I've gone through over a period of a good 40 years. Blue Coral Paste I always got in a Blue Glass Jar, but this didn't mean that the screw on metal lid couldn't rust. Also cannot even guess how many cans of wax hit the trash because of the cans deteriorating, or the wax turning to rock or going bad.
And everything else, yes everything, Slipstream, Trewax Brand, Classic, Simonize, Collinte, Private Small Company Brands, you name it, I would eventually see rust usually the lid, and the top inside rim where there was no longer any wax to protect the metal.
About the only wax I have on hand, that I haven't seen this occur, is a small 200ml Jar of UK Made Renaissance Wax, and the reason I believe it will never happen with this Wax, is it appears that it comes in an Aluminum Jar with Screw on Lid.
Given enough time, I'm quite certain it will eventually happen with any Paste Wax in a steel-tin metal Can. Humidity, storage enviornment, and as you say, dampened-wetted Applicators can no doubt speed up such a process.
It's been a a long long time since I have ever stored good wax-sealants in some hot-cold garage, or shed. Always store all of it in the house. My Spare Bedroom is starting to look like an AG-Autopia Wharehouse! LOL