Last year i cleaned two of our sticky MX-500s. They had accumulated a sort of dull thin gummy sticky film on the housing even though they're in a clean smoke-free environment and our hands are always clean. My new-in-box units are still clean.

Anyway i gathered two thin Pep Boys microfiber cloth towels, then i sprayed part of one cloth lightly with Fantastic spray cleaner (not enough to leave liquid on the remote) then i carefully scrubbed the whole casing then on and around all the buttons (using my fingernail on the cloth), moving to clean areas of the cloth as the previous area picked up the gunk. I had to go over it a few times but i took my time, but i got it squeaky clean leaving it smooth and shiny.

Then i sprayed the 2nd cloth lightly with distilled water and went over the whole remote again to remove any leftover soap film then buffed it clean with the dry part of the cloth. These things actually look like new again so it was worth the effort. Wifey thought i bought her a new MX-500 :-)