How can I synchronise signatures on multiple Macs & iPhone

Good day,

I try to synchronise my Mail signatures on an iMac, a MacBook Pro, both with MacOS X Lion 10.7.3 installed, and an iPhone 4 with iOS 5.1. I have iCloud configured with my Apple ID on the 3 devices. Is there a way to achieve this or must I do it manually?

Thank you,

Vincent Demers