On my 3 TTs that I have owned, I never use any anti-freeze to winterize.
All my TTs have had a low point on the hot and cold water pipes and have a faucet at that lowest point. I open all the faucets and let all the water drain out of the system (including the HW tank); Been doing it this way for 20 years with no problems.
You may want to look underneath your TT and see if you see a red and blue pipes sticking down with on/off tap - this is your pipe drains.
When we go camping in the winter (25F) - just close the drain tap/faucets, fill up with water when you reach your destinations and turn on the water
pump to fill the HW tank/pipes. Upon leaving, you open the drain taps/faucet and empty the system.....never had to use compressed air. I live in NJ, so we get cold temps up here.
This way you don't need to travel with a "heated" TT and waste porpane and run down your batteries.
