I've used Dave Frary's recipe for "actylic snow"

1 part Titanium White acrylic paint
1 part acryulic gloss medium (or gloss gel)
1 part acrylic modeling paste
(all these can be purchased at a craft, or art supply store)

You can apply this mixture with a paint brushy to anything...structures, scenery, etc...
It is permanent though...it won't come off what you put it on...