Although Ive never used Buckwheat hulls, I do know that dry matter at a set will remain dry so long as the thermometer stays below freezing. Its the thaw freeze, thaw freeze change that makes for tough trapping. I have used, and will continue to use Ant hill chaff as my medium under the pan, but one difference that may exist between buckwheat hulls and ant chaff, is that the ant chaff has a waxy coating on it, and any thaw moisture will not absorb into it, and therefore it doesnt matter if its freezing or not. As far as the top layer and bedding material is concerned (dirt), during the thaw/freeze period, I prefer to use a 50/50 mix of glycol and water antifreeze sprayed on the trap bed, around the edges before I pack the jaws, and then on the top dress layer to prevent freeze up. It seems to work well for this transitional period of the weather. Once the weather stays under the freezing mark all day long, I simply go to ant chaff and dry dirt, being that no moisture will wick into the dirt when its below freezing. Im not sure if this works for everyone further south, but up here we have very long periods of sub-freezing weather. (48 days strait last year at one point)