Nice. One step I would add is after restarting ssh and before rebooting while still logged in as root is to start a second ssh session, log in as the new user,

Nice. One step I would add is after restarting ssh and before rebooting while still logged in as root is to start a second ssh session, log in as the new user, and verify you can sudo. Your current instructions are predicated on success. By verifying your new user login and sudo capability before logging out as root (rebooting), you can fix typos or other Bad Things. Not that I would ever make a typo while editing sudoers. ;-)