Log on as a Service Domain GPO - add local accounts

How do I add local accounts on particular servers to a domain based GPO that is adding users to the log on as a service setting?

I can add things like:

domain\user1
domain\administrator
NT Service\All services
NT AUTHORITY\LocalService
NT Authority\NetworkService

But some servers are using local services with a ".\" like:

.\DWServer

This all started because I created a special service account that I wanted to use for a bunch if services on 20+ servers and I though it would be easy to leverage group policy to do this. Well, unbeknownst to me, this setting overwrites the local policy rather then add to. So now I am going through each server's services (thank you PowerShell!) and adding any service accounts that are listed to the GPO.

Any help in my situation is greatly appreciated!