I don't much about your unit, but FW should have separate drain valve. Open low point drains while blowing out lines, but close them before adding AF. Never seen water less drains, if they are without water I can't see them freezing. You probably only have to heed warning if drains are clogged and are going to "snake" the drain.
2016 Ford F250 XLT 4X4 6.2L
2015 Rockwood Signature Ultralite 8329SS
Nights camping in 2016: 19 nights
Miles traveled in 2016: 2,575