Another thing to try would be to grease the contact points where the shoe and backing plate meet. I had a similar problem to you this winter, only mine would only do it once, the after driving for a while and applying the breaks, it wouldn't do it again. There are 3 points on each shoe that you grease - just try to keep any grease off of the shoe surface (wipe it off if/when you get some on there). It took care of my problem, so it probably wouldn't hurt to try.
1968 Ford Mustang Fastback - Blueprint 302
1995 Ford Mustang GT -347
1993 Ford Bronco - 4" lift 35"s
2005 Lexus ES330 - Wifey's
2014 F150 Ecoboost - Boostin'