I have only ever used it on smaller pieces of fondant and I just used a paint brush/artist brush and brushed it on.
Hi Alisha, I use silver/ gold lustre dust with confectioner's glaze. You mix the dust with it and get it to the consistancy you like. I like it a bit thicker. Then just apply on the fondant. If you can see the brush strokes, let the first coat dry completley and then do another coat, till you get the desired colour. If you use this glaze, make you have the glaze cleaner too, otherwise you might have to throught the brush away.
You also can use it with clear alcohol ( Vodka ) or clear extract, like lemon. Its the same technique in applying the dust.
Liek sasporella has mentioned above, you can just dust the fondant with a brush. If you can tell us what exactly you are going to do, we can be more helpful.
HTH. 
I disolve it in vodka and then paint it on using a chuncky paint brush. Try it on some scrap pieces first, you get lots of different outcomes depending on the amount of dust and how dilluted it is.
When I first got it I tried brushing it on but it can end up streaky, you have to brush brush brush to get close to an even distribution of colour although I did eventually get an effect I liked but if you were doing something large like an entire cake I wouldn't recommed brushing it on dry.
Does anyone have any experience of airbrushing it? I have an airbrush and keep thinking about trying it but I'm concerned it would clog - has anyone tried it?
You can also dissolve it in Lemon extract. Make sure you use just a few drops of liquid with the luster dust - you don't want it to watery. Just mix until you get the consistency you want and paint it on the fondant. You may have to do more than one coat, but let it dry in between coats.
I think I have seen it brushed dry on a fondant accent - using a large (for cakes only) blush type brush. I haven't ever done it, but does that work?
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