SOLVED! For my setup anyway. I had posted same question and went nuts trying to figure this out. Floobs video is good for 1 controller but leaves out how to do 2.
So here is how it worked for me.
1.Sync the first one just like Floobs Video
2.Configure controller with retroarch
3..Above the exit 0 in the /etc/rc.local add: “hciconfig hci0 piscan” with no quotes
Now. Turn off pi.
Turn on. As soon as bluetooth dongle lights up hit sync buttons on both playstation controllers. It will take a while to sync. All the way to emulationstation.
This worked for me. But it does not work when I have wifi dongle in at same time so I take mine out. Good enough for me!
I’m using the “pluggable” brand bluetooth dongle