I want to use the [Bakery](https://www.drupal.org/project/bakery) module to login and synchronize users, but I am not able to synchronize existing accounts. http://drupal.stackexchange.com/questions/66424/bakery-users-that-exist-only-on-slave-cannot-login confirms Bakery doesn't provide pre-sync facility.

May someone help me to synchronize existing user accounts?