I've studied a course of how to 傳福音 to women years ago. Teachers informed that if the stranger is a mother, you can start to talk about topic like 育兒 with her as most mother do care of this topic including me as a mother. Then 傳福音 to her in good chance.
By my experience, I talked with mothers (strangers) on how to take care of children for several minutes while other people guess we are already friends.