A number of years ago I filled a set of 33" turf tires with a mix of WWF, the good -30C kind, and auto anti freeze concentrate, not the pre mix antifreeze.
The ratio was about 20-25% anti freeze in the mix. Both products were bought on sale when opportunity was available over spring, summer, early fall. This made the mix much cheaper than any available commercial fill available.
The "self install" on the first tire was about an hour and a half adventure. Second one was about an hour or so. Fill required minimal tools purchased. The valve stem adapter, an old 12V bilge pump, a couple garden hose fittings, and on old pair of washer hoses. The pump made a significant difference in ease of install.
By the math and charts this ratio of products would have made the mixture good for -35C range. Worked well for me.