seeding memberOf attribute

We are looking at adding the memberOf overlay to an existing deployment.

From what I can tell, after the configuration on all of the servers has been

updated, all of the members need to be removed and then re-added for all existing groups in order to get this new attribute populated?

We have a lot of groups, with a lot of members; that's going to be quite a bit of churn. I just want to double check there wasn't a simpler/more efficient mechanism before I started down that path.

Thanks much.