Hey Tom – I used to use boiling water – dipped the schnozzel valve (female) into the boiling water to soften it, then mate it to the (male) t-rest valve, and let it cool. It worked OK, but not so well when the temps dropped.
More recently, I used a little blowtorch to melt the schnozzel valve, then mated it to the t-rest valve and let it all cool.
Now it works great.
I went through the hassle of doing this because my schnozzel bag is also my in-tent dry bag for storing wet shoes, socks, gaiters, water filter, etc., so none of it freezes at night, and if needed, I can stow in my sleeping bag. Most of the time, I can sleep with this all right next to me and it stays thawed, at least if I’m in a tent and the nights don’t get below 20 or so.