Oh wow, I've used the 'snow' stuff for model railroads (Woodland Scenics I believe) but those micro-ballons and Krycell snow material look waaaaaaaaayyyyyyyy better!!!
I'm not sure I'd do the groundwork any differently than normally. If everything is being covered by snow just do mounds for drifts with plaster or paper mache. If just a light dusting of snow just do the static grass normally and sprinkle the snow material over it.