Don't often post but for our 2006 RB, we winterize by 1) drain 2) blow lines with compressor 3) add RV antifreeze (taste lingers) or cheap 90 proof alcohol and make sure it is in all lines. Do not forget hot water lines if you have hydronic heat. We live up in Truckee and it does freeze a lot during the winter. Early in our ownership we did not do a good job winterizing and had to replace the hydronic.
2006 Ford Diesel RB50 4X4