In summary, here is some cellular phone tradecraft for times of genuinely deep drama:
1.) Don't create a paper trail when buying clandestine phones. Pay cash for cell phones and don't give your name. Preferably buy them in small stores without video surveillance.
2.) Activate phones only as needed.
3.) Never "recharge" the minutes on disposable cell phones. (This leaves a paper trail--at least leading to the place where you bought a recharge "minutes" card. And buying minutes via a phone call and credit card transaction leaves a huge paper trail.)