Just finished doing our Big Country yesterday. I can share our process but a 2008 may not be exactly the same! First I drained the water tank remembering to open the check valve first! Drained the fresh water. Holding tanks were already empty. At the UDC I switch the water bypass valves to Winterize. You rig may or may not have these, hopefully it does as it makes it a little easier. I have a hose I can connect to the Antifreeze inlet. I connect it drop the end into a bottle of antifreeze (I use DOW glycol based available at Home Depot for $5.00 gal) Turn on the water pump and proceed to open each outlet (sinks, outside shower, toilet etc.) until I see the antifreeze. Takes me about three gallons as I an over cautious making sure it is running through the system. Many prefer to simply blow the lines with compressed air...I use the antifreeze. There are links on this forum with a Winterizing Checklist...I am sure someone will post it!
HERE is a youtube video of someone winterizing an Elkridge.
HERE is one doing a compressed air thing.
