Just saw your question, and although it's a late answer, it might help for the coming holiday season.
Artificial spray snow is not meant to be removed or cleaned off the surfaces you spray it on (except windows). It's just too difficult to get off. However, I came across an artificial snow product that stays loose and can be vacuumed or shaken off. Take a look at "www.sno-wonder.com" and see if this meets your needs.