If I move an Account from Production to Sandbox, then when it's time to move the Contacts from Production to Sandbox, then in Excel, in the Contact CSV, I just update the AccountID Cell with the new Account number that the Sandbox gave that account. That way, the Contact finds it's owner.
How do I do this for 100,000 accounts? I can't individually assign them all their new AccountID.
I'm just trying to find the path of least resistance and the best practice here.