Staged Migration DNS question.

I also find the readiness tests for migration harp at me to change my DNS.

We want to do a staged migration, and obviously if I change the DNS in advance, I break mail for everyone in the organization.  So I assume this refers to a hybrid migration only?  Because the MX change will direct mail away from my on premises Exchange server (if I understand priority 0).

In what order to I do thing in staged migrations?  I guess that is my question.  Do I need to do the directory sync first, then migrate batches of mailboxes, then change DNS?  And then change the local users to mail enabled?

I'll worry about decommissioning later.

Thanks!