I would like to force a specific firefox persona skin on all my domain members.
How can I do it?
There's no built in mechanism for centralised management of settings in Firefox. You're basically looking at finding where this setting is stored in the firefox profile and pushing that out with a script. Personally I think its unmanageable, but I wish you the best of luck.
On a Windows 7 machine start looking in C:\Users\%username%\AppData\Roaming\Mozilla\Firefox\Profiles\%profilename%