Making a castle cake and the top tier is fake, covered with fondant. My customer wants bling and sparkle. I do have pink pearl and rainbow dust, how do I get that to stick to the fake tier? On fresh frosting it shoudl stick all on it's own, right?

On fresh, noncrusted buttercream, it should stick okay. For the fondant, you could brush it with some piping gel or a thin layer of corn syrup and then apply the dust to it.