Wondering what coyote trappers do in cold country for preventing freeze up?

You will get a hundred different answers. Most guys go waxed dirt or sand. I use salt at some sets and waxed dirt at others. I use peat moss too. Kinda all the above for me

I'd say I primarily run peat moss with table salt till it gets down right ridiculous. Wax sand is the closest thing to bullet proof but even it fails. If it's bad enough those two don't work it's time to hang snares.

I prefer the antifreeze. I trapped in eastern Montana for years, worked good. Only problem is after a catch when the wax gets rubbed off it’ll start to rust your traps.

I believe I have tried everything known to man for deep winter freeze thaw here. Peat, cover hulls, salt and dirt, liquid antifreeze, coal dust and shale, you name it. Heavily waxed dirt or sand is closest thing ive come across for still finding a functioning set or two next couple days in deep winter freeze thaw here. I tried powdered anti freeze one year with bone dry peat and that was good for maybe a night or two but then crusted over froze up also it was hard on steel (rust).
Dry powdery dirt under bridges and overhangs were good locations to keep functioning but usually turned into coon and possum factories.
I made up 50 gallons of waxed dirt for this winter and I add extra wax to mine too. Its not perfect but best thing ive used yet. I hang cable too and run a few cat cages, just something is functioning and can save the day on catches. For dirt sets and coyotes, waxed dirt or sand is all i will run now.
I snare a few coyotes in weedy ditches and small frozen creeks.

Waxed snad

Waxed dirt sand mixture.