I have guided bird hunters across Alberta now full time for over 5 years. When I first started hunting waterfowl, I too was concerned with frost on decoys. But as I became more experienced, I soon realized that frost on decoys is not really much of an issue. Typically there are only a few days in the fall when the frost is extremely heavy (Cold, clear nights, full moon). And I have had some of my best hunts in these conditions. The problem isn't so much frost on the decoys, but the lack of frost on the ground and blinds from milling around setting up everything. Although actual birds will cause the same effect when feeding in a field, it won't be to the extent that you will create. This creates an unnatural look. Try using snow spray (Canadian Tire will start to carry it around the end of October) on your blinds. A light coating will give it a frosted look, were as a heavier coat will give it a snow look. The reason I say that frost isn't an issue, is because it occurs during cold, clear nights. Which is usually followed by a clear morning. Ducks will be your first birds to arrive to the field, most often before the sun rises, so frost in this situation is not an issue. Once the sun rises, it takes about 10-15 minutes for the frost to melt off the decoys. With morning hunts lasting 2-3 hours, 10-15 minutes is a narrow margin to get all worked up over a spray bottle with antifreeze. Obviously the other scenario is clouds move in, were of course the frost no longer becomes an issue.

I am by no means trying to tell you what to do; I am simply describing how I handle the situation.

To answer your question about decoys, when hunting snow geese. Sillosocks are going to be your best option. Motion is critical when hunting snows, as well as numbers of decoys(the more the better), followed with an e-caller. I don't find flagging snows to be very effective, a white mass of decoys is going to be more effective then waving a white flag around. You could also add silhouettes, which will add motion. I exclusively use silhouettes now for hunting Canada Geese, this will also eliminate your frost issue.