David, here is what I found: Treat in November or December, when bees are in winter ball, but on a day when temps will be above freezing, use luke warm liquid (but I share your concern about the cold), treat with 5ml per seam of bees, or about 30ml for a single 10 frame or up to 50ml for double deep. The simplest recipe I have found is 35-45g OA in a liter of 50:50 sugar syrup, which should be 3.5-4.5% w:v. I'd like to find a recipe in cups and oz's, but haven't yet.
Caveat - this is a summary from someone who has not done this yet (so anyone who knows more, please chime in), but one of the best practical explanations of this approach that I have found, and other methods as well, is at www.scientificbeekeeping.com
There is also at least one Youtube video of someone treating with this method in Germany (I think), and it looks very simple and quick.
I am going to try this method of treatement on my worst varroa infested hive (which was also my most prolific split and honey producer) in a few weeks. I hope to report good results, but I feel like I have nothing to lose, and worst case, I will learn something.