Putting all of the "social mechanisms of conversion" ideas together, it seems to me that the best way to help de-convert a religious person is to welcome them into a non-religious social circle, thus giving them the social freedom to explore their doubts without fear of total ostracism. (The group doesn't even have to be mostly comprised of non-theists, just not comprised of people who all belong to similar religions!) And if they bring up their doubts to you, it's a good time to talk.
And the best part is that whether or not it changes anyone's mind, you've just gained a friend.
(The flip side is this: avoid joining social circles where a majority are devout followers of the same religion- it will mess with your head...)
Have you ever convinced a religious person to become atheistic? How did you do this? How long did it take? Were the people in some sort of life crisis, or were they just living along?
This is probably a quite difficult task of persuasion. So stories how people were successful at it could be very interesting to improve ones' persuasion abilities.
Relatedly, it might be interesting to know what religious groups have gathered on techniques to convert people to their religion - are there some manuals/techniques floating around?