First I want to apologize for posting this on Mother's day. I have a 4" cake that is crusting buttercream icing, colors is silver and burnt orange. Silver is going on side of cake using a stencil. How can i paint the buttercream design with the silver?

Mix the dust with something like vodka or extract   Look for the alcohol content—the higher the better  you want the mixture to be just fluid enough to be allow it to flow off the brush   Also you need to work quickly as the alcohol will evaporate-if it does just add more alcohol   If the gold is streaky there is too much—let it sit a few minutes so the alcohol evaporates Some  

Just vodka? This bottle of paint needs vodka? I guess I'm confused. This is what I have. If I use this will it cover the buttercream? I'm going to be using a stencil on the side of the cake. This is a first for me. 

 Not exactly sure-that is not dust   Guess you will need to make a test   Just spread some icing on anything & using a soft brush paint some on   It should go on smooth & not splotchey & not come off when touched after a time of drying 

That probably doesn’t need vodka - I bet it already hhas a good amount in it

And yes it should easily cover buttercream 

I use that paint on fondant. I think it would work fine on crusted buttercream. I would use a sponge to dab it on and don’t go over the same area more than once as it will come off. It’s water based so takes ages to dry. 

Or a paintbrush would work but again don’t go over the same area twice as it seems to pull off. 

Since it's a holiday I'll start testing it out tomorrow...I'll let you know!

Glad to see someone who has used it help you :)   Never thought about using a sponge— good advice