How do I achieve this? My daughter wants a mermaid cake and the mermaid has metallic teal, purple, gold, pink, and silver. Do I just sprinkle on luster dust? Is that edible?

The best way is to airbursh on the metallic color. If you do not have an airbrush, then mix luster dust with a small amount of clear vanilla or vodka and paint it on. If you use purple luster dust, you must mix the purple with clear lemon extract in order to achieve the true purple color. I am a Wilton instructor and this is something that the Wilton execs have passed down regarding the purple luster dust. All the other colors are fine and stay true to color when mixed with vanilla or vodka.

If you don't have an airbrush I have found that you can add nu-silver luster dust to a color gel and vodka or an alcohol based flavoring. The silver will add the shimmer and it can be brushed on using a soft brush.

See my post in this thread:
http://cakecentral.com/cake-decorating-ftopict-608716.html