Bill, I opened it up to do this to the 9090. If you just run the contact cleaner down the switch, the liquid will mostly be absorbed by the felt washers that these switches have fitted to them just below the slots that they pass through, then it'll all evaporate away before it has the chance to go to work on those dirty contacts.
Thanks to the logical way Sharp assembled these lovely old boxes, it's really easy to get right to the exact spots where switch spray is needed, in this case right into the switch.