If you have an airbrush you can use the airbrush pearlized color. If you dont, there is a company that sells a can of pearl spray that looks almost like an airbrush.
Dust wont work on buttercream, only over fondant.
Hope this helps, thanks so much for the complements!
Edna 
I've sprinkled edible white glitter on cakes and it looks nice and sparkly.
Dust wont work on buttercream, only over fondant.
Why don't they?? 
I have airbrushed pearl dust and luster dust (mixed with everclear) on buttercream cakes. I've even dry dusted the top of one buttercream cake with luster dust.
I think they have white luster dust? It would be shinier than pearl, or you could mix the two. Actually, I have added nusilver luster dust (powder) to pearl dust (powder) mixed with alcohol and sprayed it on with the airbrush and it was nice and sparkly! I don't like the pre-made silver airbrush spray as much, it's too wet, using the alcohol makes it dry more quickly and doesn't affect the BC as much.
Also, you can get a shaker of this: http://www.pastrychef.com/RAINBOW-SPARKLES_p_1550.html
I love this stuff...very prismatic, rainbowish and catches the light like diamonds.
Dust wont work on buttercream, only over fondant.
Why don't they??
I have airbrushed pearl dust and luster dust (mixed with everclear) on buttercream cakes. I've even dry dusted the top of one buttercream cake with luster dust.
I am not talking with an airbrush..I have done it like that too! 
..I meant in a dry stage where you only use the powder dry and a brush. And is not that it can't be done, I just dont like how uneven it can be..
Edna
Wilton makes a product I think you are looking for. It is called Cake Sparkles. I found it in the cupcake section. They are like small flakes of glistening sugar. Not as fine as a luster dust. More like mini mirror flakes or like mica. Beautiful and can look very nice. I used the navy color for a solar system cake to add sparkle to the cake. It is more sparkle than luster.
Be careful with the timing, however. I used the Wilton cake sparkles for a snowflake cake...put it on in the morning before work and by the time the office Christmas party started 4 hours later they had dissolved into the buttercream and yes, it was refrigerated.
I am not talking with an airbrush..I have done it like that too!
..I meant in a dry stage where you only use the powder dry and a brush. And is not that it can't be done, I just dont like how uneven it can be..Edna
Ahhh okay, read it wrong before.
I've dusted them on dry, it can be done, but like you said it can be uneven and you have to have a very light touch.
I'd much rather pull out the airbrush.
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