Cisco Support Forum suggestion
Having been asked again today, I would say the sort of official recommendation is to restart your publisher server first and wait for it to fully recover. Then repeat the process with each of your subscribers. My thought was obviously to always retain as much phone service as possible by rebooting and recovering each individually, but frankly I don't know why the publisher should go first. If you have one freshly rebooted server to rehome to, what does it matter which one?
At least Cisco confirms that I'm not missing anything (see link above).
Of course something in version 8 will likely explode if you do so in the undocumented correct order ;)