Anyone know how to achieve this? I have a bride wanting a silver finish on a cake pop but what will stick to white chocolate best? Airbrush spray, dust w/luster dust, any ideas?

Do you have time to do a little test? I'm pretty sure luster dust or luster dust dissolved in alcohol will work, but the airbrush finish would probably be more silvery (although I'm an airbrush novice, so I could be wrong about this). Do you have time to make a small batch and do a few of each to see what would work? You could take lots of photos to document the whole thing so you could file it away for future reference (and, of course, post it here so we could all see what happened, hint, hint).

Karen of Pint Sized Baker has used dry luster dust on some of her cake pops. She has a video tutorial showing how she turns white cake pops a metallic copper with the luster dust.

Luster dust brushed on dry sticks very well to chocolate. No need to add liquid.

Luster dust dry brushed on does work just fine for metallic finish on cake pops. To help this along I tint the white chocolate a base color of whatever metallic shade I am going for. Then, make sure to use certified food safe luster dusts (i.e. Crystal Colors). Here is a picture of some cake pops I did recently in this manner.