Hey all -- here's my experience. I couldn't get any of my Sony Dualshock controllers to sync, even in the Classics mode..! They would work wired, but never would sync wireless. I went to Restore System Settings. I reset my audio to optical, etc... I let my newly synced controller connect wirelessly. Then here's the steps you have to do:
(1) Hit SELECT+L2+Triangle to ensure the the PS2_Classics file is enabled (triggers from Webman Mod -- Thanks Aldostools).
(2) With the controller now wireless, fire off the PS2_Classics that you have already set up from the other tutorials. It will run... and lo and behold, it synced wirelessly now! I never had to replug it in USB. I also tried to sync my 2nd and 3rd controllers, but they would NOT sync wirelessly. So much for two player PS2 games (wirelessly)!
(3) Quit game -- go back to XMB. Now hit the SELECT+L2+Triangle combo again to disable PS2 Classics.
(4) Run cMMan and mount the ps2 iso normally.
(5) Run from the PS2 Classics icon. Now the ISO that you mounted will run, and it will still sync wirelessly. Again, I was unable to get more than one controller to sync wirelessly, even in Classic mode.