What I've done with the lens covers on
Posted by: g2d on Feb-18-13 3:33 PM (EST)
my ancient Minolta Weathermatic 35, and on the waterproof case for my digital Canons, is to blow really hard on them and then give them a moment to dry. In bad circumstances, I clean them with the tip of my tongue, slosh the camera in the river, and then blow to clear off residual drops. I haven't had a problem with the lens covers wearing, not even the coated cover on the Canon waterproof case.
It helps if the lens cover is large enough. A small cover can be hard to clear with any method.