I can help a little on the product to use, but I'm not familiar with how the plumbing system works in your new coach. If it has an on-board fresh water and pump I may be able to help.See below
I use this product, however I think most RV antifreeze products are good to -50° I get mine at camping world, but Wal-mart also sells RV antifreeze.
If your rig has a fresh water tank then most folks blow the system out will an air compressor regulated to 45# of air pressure. Hook it into your city water hookup. Flip your water heater bypass and drain the water-heater. Then go into the coach and open each faucet individually to blow water out of the system. Flush the toilet as well. Quit when you are getting mist from the faucet, shower head or toilet. Drain your fresh water tank and then refill with 3 gallons of antifreeze. Flip you water supply over to your on-board fresh water and then turn on each faucet, the shower head and the toilet, until pink antifreeze is running out. Run it long enough to get at least a quart of antifreeze into the drains P-trap and into the gray and black water tanks. You should now have antifreeze into every place water flows.
Some folks can skip the blowing out and just drain fresh water tank and then add antifreeze, however you are in an extreme climate with temps to -40° so blowing will assure that you haven't diluted the antifreeze to a level that could cause you some issues.
Hope this helps.