I just re-sprayed the dual controls of our 206 at our company. I took a risk and used a light sand paper to remove a layer of gunk that had acumulated on the cork grip. I then covered the grip with masking tape and sprayed the rest of the surface with matt black spray apint. They look brand new now. I even went to the extent of taking tip-ex and running it into the grooves where is sais "Open/Close with the arrow"
Let me know if I can help at all. Just make sure you use the right colour of black...