Going back to the technical, this zine is a (mostly correct IMO) guide for setting up a burner phone. Some people might feel they need their phone for actions. Maybe they do. Maybe they don't. If you're going to try to set an anonymous phone, this is has information to consider before starting.
https://ia802707.us.archive.org/12/items/zines-security/How_to_Set_Up_a_Burner_Phone.pdf
If you're using digital comms, signal and phones might not be the best way to communicate. "The Guide to Peer-to-Peer, Encryption, and Tor" covers alternative messaging apps and why you might use them.
https://itsgoingdown.org/the-guide-to-peer-to-peer-encryption-and-tor-new-communication-infrastructure-for-anarchists/