A group PM is rather simple, just click on the PM icon under one of us(clear the message box before writing the PM), at the top there's it'll say "To:" with the name of the person you clicked to PM, right under that is a box, write the name of another person then add(just like you would with adding characters to posts, it's uppercase sensitive).
So yeah, I was kinda expecting this needing to be revived. So first of all I made a pad:
https://public.etherpad-mozilla.org/p/The_Catalysts go to it, favorite it and set up your name and color to preferences. Pads are amazing, it allows people to work together if they are online at the same time, and it can also be used in the same manner as the OOC, it makes brainstorming a whole lot easier and allows for more collaboration(such as colab posts with less repeating of what another character did or said, because it can be compressed to one post).
Then here's some of the beta test feedback(which will be copied to the pad so we can make a clear list of feedback, I'll clean it up later).
Like you said the factions came down to being nothing but a distinction between us and them. This likely is caused by the fact that each faction is rather empty, and that there are too many of them. My suggestion would be to cut a few of them off, Devils hand, Mana charitable and Hunters blacklist seem like the most likely candidates, and get a couple more characters for each faction going(5 or more per faction I'd say). It'd leave one terrorist group, the government organization and the vigilantes as factions. The three factions that'd butt heads most frequently, that combined with some factionless or minor faction(such as a religious zealot minor faction, and a couple of teamed up mercs) characters should create a much nicer mix.
The lack of organization within the faction tends to cause problems too, I do appreciate that you are using hands off approach allowing the others to carve the story just as much as you, but it simply doesn't work if there isn't a guiding goal. The entire arc so far has been leaning on the first event, it's aftermath and the activity of certain characters(Vanessa), who I'll probably often refer to as plot devices. While this does work, it means you need a whole load more characters like Vanessa, even if Devon had been able to go to work like I'd planned it'd still be too few for the amount of factions. With only three major factions though, it would likely be enough.