I recently got a great reply to my windshield wiper question - But I have a follow up question. I was told to spray the switch with WD-40 - do you mean the actual switch in the car that turns them on? I know this might be a stupid question, but cars are not my specialty, and I thought I would ask before I sprayed everything...

You will likely need to remove the covers, referenced in the link, to gain access to the switch mechanism. Then, just spray the switch with WD-40 or electrical contact cleaner.