I have an easy way to get rid of them without being rude. I just ask how much they're paying participants.Have you watched Lord of the Rings? Towards the beginning, Bilbo Baggins says "No,thank you" when Gandalf is at the door. It's not impolite, just definite, with a hint of English Professor. ;-) I've found that a "No, thank you" expressed using precisely that tone will immediately shut down even the most persistent caller. ;-)
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
