Believe it or not, with silk flowers, I often take the arrangements apart and, holding the flowers by their stems, give them a few fairly hard shakes to get rid of the dust. I've even whacked them against my hip. Once in a while, a leaf will dislodge; but, so far, the damage has been minimal. You can usually tell where something came off and put it right back in that spot. I've also successfully tried rinsing them, but that's more time consuming; and it only works if the stems are plastic.
Of course, you do this at your own risk. I'm not guaranteeing you the same results!
