Yamaha DTXpress/DTXplorer/DTXtreme

Hello all, 

Can someone please tell me the best way to clean the rubber pads on 
my DTXpressIII sp. I've tried just using a damp cloth but it doesn't 
seem to work very well. My pads look like they have a fine layer of 
dust on them but I can't seem to get them looking new again.

Thanks!

Ken B.