Good Morning all, hoping you all could help with a few last minute questions before I dive into doing my DDs cake for Tuesday. My plan is to start it tonight after work (cakes are already baked and froze) and took tomorrow off to finish it up after the kids go to school. I have a few questions first.

Painting rock candy...can I just use the usual vodka and food coloring or will the vodka eat away at the candy? 

The gold border?...how do I do that? I heard it can be made with just vodka, powder sugar, and luster dust. Anyone have experience with it? 

Third....is it possible to marble/pour ganache to make a marbled effect? Can I color it adding the coloring to the cream or will that seize it? I meant to experiment this weekend but FIL made a surprise visit so my weekend consisted of cleaning all weekend.

Help please. Any advice tips or things that helped you would help tremendously. TIA!!!