Lots of opinions on winterizing. I will try to be brief and at the same time put forth an opinion on BOTH sides of the dry winterizing / wet winterizing process.
You can just blow out the lines with air.
Do not forget to open the "low point" drains.
Do not forget the "P" traps. You still need to pour a little RV antifreeze into those (sinks, shower/tub, toilet) or somehow make sure they have no water resting in them.
Do not forget to drain the fresh water tank.
Do not forget to drain the water heater (remove the plug and lift the pressure relief bail).
Some people use RV antifreeze and then blow out the lines (double sure).
2011 Georgetown 337
2009 HD FLHTCU
2007 HD FXSTC