Are they white chocolate clay? If so, I am assuming it is similar to fondant (never used it before) and you can paint on it the same way. I just use vodka mixed with my luster dust and paint it on that way. Just don't use to much or it will be too thin. Or if you want a more subtle look, you can just dry brush it on.
HTH,
Heather
The best way to do it is drybrush it. If you look in my pix I have a chocolate heart cake with chocolate buttercream roses -- which were very stiff in consistency, similar to your chocolate clay. Check out Mich Turner's book "Spectacular Cakes" and she does the same thing, drybrush on chocolate clay. Hope that helps some! 
Just out of curiosity, can you paint the luster dust on a buttercream rose??
Just out of curiosity, can you paint the luster dust on a buttercream rose??
Yessirreee Bob!! If you look at my pix, on the monogrammed cake I did that (but quickly scrapped the idea in favor of drybrushing). On my www I have a similar gold rose cake where I painted them too. The problem with that is that it makes the rose gooey. If the rose has crusted over and/or is chilled/frozen, if you work fast you won't make it gooey or deformed (like painting with a liquid mixture tends to do.) 
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