If all your characters are running from the same instance on the same computer, then kiss will buff them all from every character setup to buff. If you are running multiple groups on multiple instances/machines, then turn on DanNetOn and any character using DanNet will get buffed.
Last but not least, you can add characters to an extra/external list for buffing. The /tbmanager command can be used to add or remove characters to/from the list. Names are never stored in kiss, so the users ID is stored for reference. Use the command as follows:
To add your target to the list.
/tbmanager add
To remove your Target from the list.
/tbmanager remove
To add a character character NOT using you target.
/tbmanager add ${Spawn[pc CharacterNameHere].ID}