I've never added pink stuff. I only blow my lines out. I open all the lines and blow for a few mins. I do open the low point drains, fresh water tank drain and empty the hot water heater prior to blowing. Haven't had a problem in 6 years. I live in Oregon and we don't get that constant really low temps in winter. I have other friends that just blow the lines and none have had issue either.
IMO it depends on where you live. I certainly wouldn't blow the lines if I were adding the pink stuff. Like mentioned it seems redundant.