Would a couple
of drops of de-ionised water around the switch help? (just enough to free it slightly, then use the switch continually for a couple of minutes in order for free movement)
Then place it switch downward to stop anything getting further inside, on absorbent paper/towel.
You could maybe try it a couple of times? Using silica-gel afterwards might be a good idea too.
This is just a suggestion from a luddite & maybe not recommended, so don't hold me responsible if owt goes wrong!
I also thought about the smallest
squirt/drop of WD40?
btw,He who dies with the most toys, WINS!Nikon D800E & D700 bodies + Nikon 200-400mm F4 VR1, 50mm F1.4G, 16-35mm f/4G VR, 105 F2.8 VR macro, 70-300mm lenses. A couple of filters, Giotto tripod & ballhead. Lowepro Slingshot 302 AW