I live in Central Texas, so freezes usually are weather getting below 32 overnight. Knowing this, I blow the lines out, then pump in some cheap vodka, then blow the lines out again. The drains/traps get RV antifreeze, and I call the job done. The benefit of this over the pink stuff in supply lines is that after a de-winterizing, there are no lingering tastes/odors. I also bypass/drain the water heater, since that is a good time to replace the anode rod anyway, although here in central Texas, the rod stays almost intact, except that lime builds up on it, and if not scraped off, may render the rod too large to be removed from the water heater.
However, if I lived in a cooler climate, I wouldn't take chances. I would dump the tanks, dump/bypass the water heater, blow the lines out, add pink stuff until it came out every faucet, blow the lines out again, and call it done. Just blowing out the water has a good chance of leaving stuff in low places (especially valves and elbows) which will crack over the winter.