Funny thing this, i always got the idea, any of the snow effect on the Hoth filming mini's wasnt a permanent fixture, take the Probe Droid for instance, that was dusted in some shots, yet the model today looks very clean.
Id gamble the Taun was the same, it was a dusted layer possibly that was re applied as and when, this making this a harder subject to tackle, but id still go for scenic snow, its the best option ive seen Guy.
As for application, id maybe go with a spray bottle for the adhesive (thinned down to very a very thin viscosity), then dust it down as needed? Bit of a head scratcher this, as you dont want to cheapen anything, which is where, id go for a dry dusting for display?
lee