Quoted from BigB:Try graphite powder first. There is a reason that you should never use any type of oil or grease on a pinball machine.
In a recent conversation with a locksmith, he said that graphite gums things up over time too. He hates when he opens a lock and finds it crammed full of "blow in" graphite.
So, there you have it. The opinion of one guy who you don't know relayed second hand through another guy you don't know. Pretty legit I think.