AIt looks as though it has been airbrushed with one of the luster dusts. Americolor makes a line I really like.
The cake is absolutely beautiful.
I've seen some like this before where they used a large paint brush to apply luster dust paint to get the texture you see on the top tier.
AI have also seen a tutorial can't remember where but they use a very large paintbrush and in affect paint the lustre on. You will need to have super smooth fondant because the lustre magnifies any imperfections on it. I'll try and find the tutorial and post it if I am able to
Here's the class to learn how to make this actual cake, only $695 
http://www.bakingarts.net/class-popups/popup-introweddingcake.html
And here's the class with the original instructor, if you live in Australia.
http://fayecahill.com.au/workshop/glamour-finishes-3/?event-categories=upcoming-workshops&page=1
But, yes, you can do it with a brush. There's a thread here, where someone explains a bit how she did it.
http://cakecentral.com/t/56728/paint-fondant-and-use-luster-dust
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