I was looking at the ghost hunter interactions, and noticed that a couple of the interactions for ghosts give 1/4 bar jumps in relationship for each one. Recalling that the charisma challenges don't care if the 'friend' still exists once the friendship has been made, I ran a test by making a ghost hunter with a single point of charisma learned.
Sure enough, after only a couple angry ghost jobs, I had the Everybody's Best Friend challenge completed, and a good chunk toward all of the others save the joke related one.
Sadly, since the ghosts cease to exist after moving on or being captured, they don't count toward the charisma skill requirements.
Just thought I would share my observations.
