We live in the SF Bay Area, so, as far as minimum temp goes, most winters we get a few nights in the mid to high 20s; every couple years we might get a couple nights in the low 20s . . .
That being said, we have always used the simplified blowout method (first method in the following link). With that method you don't put any pink stuff in the fresh water side, only down the drains/toilet tank, etc. There is a some risk that low spot water in a valve or some other place, might not get blown out, but we are very, very thorough with our blowout until absolutely no water mist at all is being blown out of any fresh water outlet. We've been using that method for 12 years with our Toyhouse and, in our mild climate, we've never had a problem.
Again, it's the first method here:
http://rvroadtrip.us/library/winterizing.php