When I was growing up in the late 70s/early 80s I had a good friend who's father was a now academic but fairly fire and brimstone 6ft 6in tall Church of Scotland minister with a strong Glaswegian accent and who was also an avid collector of handguns and shotguns. He never wore a dog collar out of work.The knocking on doors tactic was more irritating than anything, and often led to some parties coming up with creative ways to get rid of them.
I may or may not have used some unorthodox tactics to deter future visits from the JWs back in my uni days.
He used to invite JW's into the house and then evangelise to/ harangue them at length about theological issues whilst cleaning one of his (dismantled) guns. They got the message after a few occurrences of this and left the house alone after that.