Who is your audience? Witnesses still in? Elders? I think the most effective way to break through people still heavily "in" is to drop questions and wait for them to respond. They won't open anything not written by 'mother'. I refer my JW hubby to the Encyclopedia Brittanica because that is the only material, other than the society's, that he trusts.
As for flyers warning the public away, go for it! I think a very short flyer insert in magazines at the laundromats would be a fantastic preventive service.