I haven't done anything big but this ardennes stretcher bearer was micro baloons over plaster/white glue if I recall

Well, the last two I did, this one was Woodland Scenics 'snow' over plaster. 

This second one was styrofoam as a base which I carved a little to get it uneven.  I added a little plastic cement with a brush in the footprints and in the tank tracks since it dissolves the styrofoam. I then added a light coat of Green Stuff World 'Snow Powder'. I think it looks a little better than the Woodland Scenics stuff though either will work. 

BTW: That looks great John! I haven't tried micro-ballons yet. 

AK actually has products now - I did that figure years ago before AK existed.  Products look great though

https://www.youtube.com/watch?v=7kPMOIz4_cs

Those were some great video's keavdog. Thank you for sharing them. They will be very handy in the future for me. Again thank you.

      The fellow looks a wee bit like JFK in the face!

Baking soda will yellow over time; I would avoid it.

Microballoons are a good suggestion.

I've used Micro Balloons and Woodland Scenics Snow and would highly recommend using either one. You can't go wrong. Here are two of my examples.

Looking good!

I tried using Tamiya snow once. It turned out ok, but it was very hard to work with.

S.H.