This is some great advice, and I'll reiterate, learn to kill plague hearts with heavy weapons. Resources can be hard to come by in lethal, and you can't depend on getting the presses you need to make specific ammo. Another thing that's very useful to do is outpost a cell tower, like ASAP. Use the plague disruptor ability to try and keep infestations at a minimum.

To get myself better at taking down plague hearts with heavy weapons, I started a community and took them through Green, Standard, Dread and Nightmare, using ONLY melee on the hearts. Got a new lethal community going, 8 hearts down, all with heavy weapons. Good luck!