Ken,
Great Work.
I too have discovered the marvels of Woodland Scenics "Snow". Let me share some of my observations.
First, I mix the snow with Modge Podge (a white glue like substance used in decopage) and make a paste like mixture. This can be troweled onto the tank, between bogies, on fenders or any area with little foot traffic.
Second, take the same mixture and add acrylic burnt umber, some ground cover (fine ground sawdust) and you ger "mud". The mud can easily be applied to tracks lower hull surfaces and will dry to a shiney/muddy look.
One thing about using the paste is you can create drifts, and with some practice icecicles.