well, if your chosen users are already in admin or super admin, then you could simply go the users table via phpMyAdmin and run an SQL statement: UPDATE `jos_users` SET `sendEmail` = 1 WHERE `gid` = 24 OR `gid` = 25
This will make all your admin-superadmin users moderators.
[you might want to check in your jos_core_acl_aro_groups table that 24 and 25 are the correct id's; they are the default values]
If you want to be selective about which admin/suoerasmin users you upgrade or you want to upgrade your chosen users from a lower usergroup, then you could edit the 'users' table by checking all the users you want to be moderators, choose the 'edit all checked' option (the pencil at the bottom) and set the 'gid' field to 24 or 25 {admin or super admin) and the 'sendEmail' field to 1. That would do it - you have to edit each record but they're all there on the one screen ...