Glad you found the right size tool. I always disconnect the battery when working on electronics. And the air bag IS an explosive device.

After loosening the two torx screws, lift the air bag up and disconnect the connector. Store the air bag face up. I've been told not to turn on the key with the air bag disconnected as this will cause a code that can only be cleared at the dealer.

If you can't find the source of the rattle at that point you may need to remove the steering wheel. The mounting bolt (10mm hex ?) can be very hard to remove since most are put on with thread locker. I had to heat mine with a butane torch to get it free. [Not for the faint of heart.]

Hope that helps some. Good luck.