in addition to a username/password for a sync account, you need to use an (unretrievable) sync key to add a browser. i understand the desire for security and privacy, but this is just horrible usability. i can get it all working obviously but there's no way this person (who is 80 years old) is going to be able to enter a key to set up the remote machines.
chrome's sync is much better. just use your gmail/google account credentials, and you're all set.