BetterPrivacy add-on for Firefox
>> Previously, the only way to delete Flash cookies was to use an online settings panel that was confusing for many users.
The BetterPrivacy FF extension has always allowed you to manage your LSOs, and in a very granular way. You can delete them all manually, or selectively, or periodically, with options to clean out LSOs when you start FF or quit it. Recently I've also seen other FF extensions like Ghostery include wiping LSOs too.
I never trusted Adobe's online settings panel. It had a quirky interface, required you to actually be online, and relying on a company like Adobe considering their history of security and privacy issues take a great leap of faith.