I finished listening to the first part of his Early Christianity to Constantine from the Teaching Company. It is a survey course. He explains that he is certain early Christians did not go around knocking on doors or curtains. There were no large missions or tent revivals. Rather, it spread word of mouth. He cites Paul as the best example. When he enters a city, he sets up a business which leads him to acquaintance with many clients. He talks to them one by one about why paganism is wrong. God is all powerful. What is more he saw the dead Jesus himself.
Christians had very bad reputations fueld by the ignorant. Yet one of the earliest references to Christians concerns an outbreak of the plague. Christians willingly stayed behind and nursed the sick of any religion. So along with incest and cannibalism at night, Christians had good deeds to attract more followers.
This is very different from the WTBTS