Spreading another Civ's religion? I'm new to Gods and Kings, and in the game I'm currently working through, I didn't manage to found a religion of my own. At this point, My cities are split between 3. 

 Is there anything I can do to influence which of the foreign religions becomes dominant for my civ? If I spawn a missionary from a city that is Jewish, for instance, can I use him to convert my other cities to Judaism? 