Get down to the chemist/pharmacy or whatever you call it, wherever you are, and get a box of Epsom Salts, also called magnesium sulphate. Brilliant stuff for scale snow!
Stick it on with white glue (try a test piece first) leave to dry & then spray lightly with a couple of coats of gloss varnish.
It's cheap, and is used to erm, clean out your insides, if you get what I mean. So make sure you wash your hands well after using it, you do not want to find out how well it works!
With careful handling it should stick to your diorama's during transport.