How to assign service domains to multiple users classes ? (4298759)

Currently it's done manually assigning service domain by User options > User maintenance, selecting a user and clicking on button "Other information" and then with "new" button defining a "service domain" and "user class" for a particular user. This involves a lot of manual effort and time. The target is to reduce this manual effort and time to assign the user class to a Service Domain if there are multiple users with the same classes and same Service Domain. How to assign service domains to multiple users classes?