If my Leica gear has been subjected to rain or a high humidity environment, I get one of my silica gel dessicant packs, put the camera and/or lens in a gallon size ziplock bag with the silica pack, zip the bag closed and leave it sit overnight. The silica gel will absorb any moisture that may have gotten into the camera or lens.
You can get these silica dehumidifief packets at
http://www.silicagelpackets.comThe 40 gram silica pack that is in a 2"x4"x1/4" perforated aluminum container is a good size for photographic applications, as is the 45 gram 2.25"x2.25"x1" plastic container.