Migrating a Blogger Account to a New Email Address

 What this excellent page doesn't tell you is :

The new email that you send the invite to has to have an associated Google account to be able to login with. That's no big deal - when you go to sign in, you just create the new account.

You have to suffer the "Create new Blog" stuff when you DO sign in. Never mind, just give it some placeholder name and click-through, and then you'll see this blog and the old one which you can switch to.