Yes, I agree that asking them to hold something filthy is a good way of getting them to leave.
My neighbor found me changing the oil the other day and said, "Whats wrong with your CAR??" and I told her (from underneath it) that I was just changing the oil before a trip. She said, "Oh! You actually do that?" And then went on to tell me some ridiculous story about something or other. Fortunately she just wanted to talk, not be responded to, so after a while she stopped, said bye, and went inside. Crazy people...
peace,
sam