if you don't want to go for the gw snow flock, you need to invest in some "bicarbonate of soda" you'll find it in supermarkets in the home baking area, not to be confused with baking soda , two different things. mine cost 89p did 2400 pts plus movement trays with 1/2 tub
instructions;
mix the bicarb with pva glue (cheap and nasty stuff, wood glue will make the snow turn yellow and nobody wants yellow snow!!)you want a thick grainy paste, add a little white paint emulsion or kids stuff is good, this helps give some depth, if your glue dries too clear you''ll have dandruff bases.
Dab some white paint where you want the snow to fall , then dab your paste, to finish dust some more bicarb and shake off the excess et voila, i'll be at the club tonight hanging aroun i'll bring a movement tray