Adding users to Sharepoint when they are not in the same domain

Bear with me as I explain this, I'm working my way through Sharepoint access as I go, but I'll clarify my question as I go along.

The Problem We have about 10,000 users who need access to our Sharepoint 2005 based reporting. Because our organization is migrating from one domain to another, we need to add each user twice, once for each domain. For the current domain, this is no problem, we've got a powershell script that I tweaked to add all the users in a given CSV file, this takes about 5 minutes to run.

The big problem we're having is with users who are NOT in our currently active domain. Because the sharepoint server cannot authenticate the new users, we can't add them directly. What we're doing is creating a temp user, then using STSADM.EXE to migrate that test user to the proper domain/user_name for each of our 10,000 users. The creation and migration takes about 5 seconds per user, or well over 12 hours to run.

The Question

Has anyone encountered this before? Is there a way to add users without requiring AD authentication? Why is STSADM.EXE running so slow?

Thanks a lot for any advice or direction anyone can give me.

From serverfault $pageUsers[$entry.posts[0].author].name

• Wouldn't it be a lot easier to create a trust between the two domains?

  Chris Thorpe : This seems like the right way to go. You create a domain trust between the domains, and make sure sharepoint can see both. Then you add the users in fully qualified e.g. olddomain\username or username@olddomain
  From Massimo