Snow-makin' doog here!
Actually, using talcum powder for snow effect is very easy.
Remember that all you have to do is to provide the illusion of snow, and the illusion of depth. The talcum powder only provides the airy, light top; ie; the fallen "flakes" of snow. So just sculpt your "snow"--with ruts, drifts, whatever landscape features you want, with Celluclay, plaster, etc (your regular choice of ground material)----and then lay down a coat of white glue and gently sift on the talc. Seal the first layer (when the glue is dried) with dullcoat, and then while the dullcoat is still wet, sift on more talc, and you're done. You can reapeat the last syep if you want for "insurance"; when everything is well-dried, errant talc can be cleaned off surfaces where you didn't want it by simply blowing, brushing, or using a brush wet with water to wash it off. Trees, grass, vegetation can be snow-coated by simply spraying with dullcoat and sprinkling it on and then re-sealing. I used this exact technique for this dio:
On a related note, Kykeon pointed out that talcum flakes are "flat", as opposed to silicate "balloons"...and when I think about it; that is also the shape of snowflakes ; silica balloons are round, and snow is not. It's always bugged me a bit when I see a snow dio made with those round "snows" because it doesn't look real to me...just my humble opinion; but try both, and see what you prefer. I haven't tried a mix of both, but that sounds like it may be even more attractive, because of the variety of texture.
Good idea for the next one!....