I found the solution for getting 2 controllers to work at the link below. Reposted here for convenience. I'm still looking for a way to pair 4 PS3 controllers.
LINK
https://www.reddit.com/r/RetroPie/comme ... s_through/
Above the Exit 0 in the /etc/rc.local add:
“hciconfig hci0 piscan”
This forces the bluetooth scanner to continue to scan for connections after it has connected once thus allowing a second controller to connect.
A couple other helpful links
http://blog.petrockblock.com/forums/top ... ustration/
http://blog.petrockblock.com/forums/top ... th-how-to/