Accualy, EJ, The passage about shaking the dust from your feet refers to an entire city that is unwilling. This is a (symbolic) jesture that you would not want to place on a city if anyone belived. That beliver will have friends that won't belive, and you don't want to say something about anyones friends. I get the idea that shaking the dust from your feet was a rarely done thing. (I only recall reading about it once)

I don't know how much door knocking was done early on, but we do have record that the apposles would stand in the town square (equivelent, towns in those days often had a central place where the mayor would daily annonce the news, and the rest of the day anyone could use that place)