It gets plenty cold here in central New Hampshire and I've NEVER needed to use the coolant hose heater on my CK20. I have cleared snow in -20F and she started just fine and worked it's heart out after idling for a good 15 minutes.
My starting procedure when it's cold is straight from my dealers mechanic.
-Turn the key to start the glow plugs (only once NO cycling the plugs multiple times)
-When the light goes off, turn the key to start
-As soon as the engine turns over - TURN THE KEY TO THE GLOW PLUG SETTING AGAIN so the glow plugs are on.
Since the engine is running, the glow plugs are not relying on just the battery for power so you won't be draining your battery and they work better.
You should only have to hold it on the glow plug setting for 2-3 seconds and you will notice the rpms smooth out. Works like a charm every time!
It's tough to put it in words, I should just make a video of me doing it...