Your father’s approach was good.
My mother was more subtle. She’d invite them in, give them coffee, cookies, and a LOT of small talk. She’d act all interested and naive. This would go on for maybe an hour or more I came home from school one day and that’s what was going on. I asked her what she was doing. She said that if they were there with her, then they weren’t bothering other people who might actually be interested.
When it was about time for Mom to call an end to the session, she’d tell them. “I understand. That’s what my husband preached about last Sunday.” They couldn’t get away from that preacher’s wife fast enough.
This one time I had Mormons show up at the door... I invited them in. It was a trap.
I quickly exposed that, after they agreed that they followed the Ten Commandments, that they couldn’t name more than six of them. The next two hourse were me giving a religion lecture to them.
I invited them back for another session but they never took me up on it for some reason.