Confusion around adding additional Trusted Phone numbers and Devices to a Developer Account

I am confused about how to add a trusted phone number and trusted device to my company's main Apple Account, the one who is the Account Holder.

I understand that we need to:

1. Obtain an iOS device that is associated with a phone line.
2. Create an Apple ID that is controlled by my company.
3. Add the Apple ID to the device.
4. Set up 2 factor authentication.
5. Sign into

https://appleid.apple.com/account/manage#!&page=signin

with the new ID and select Account Security.

1. Then select to add a new Trusted Number. Enter the phone number assigned to this new device and continue.

Now we have a backup account and device that can be used to access the account if the Account Holder or the device associated with the Account Holder is not available.

Is this correct? Do we have to have a device that has a phone number? Someone suggested that you could use an iPod Touch as a second device, but you cannot assign a phone number to an iPod Touch, right?

I am very very interested in following best practices with regard to this and would appreciate any information or links to information on best practices.