Ignition Gazebo control topics for UAV?

Hi - I am trying to figure out how to send commands to a UAV (the X3 or Marble) in Ignition Fortress. I spawn the model in the world, and an ign topic -l shows the sensors, and I can echo them. I can’t figure out what the control topic is though - I don’t see the equivalent of a Diff Drive controller for the multi rotors. Any guidance or pointers to a tutorial/document would be much appreciated. Thanks!