How to tag marked locations to complete Protect/Destroy in Marathon

Once you complete Order/Chaos for MIDA in Marathon, Gantry will give you the Protect/Destroy contract, which has five steps. In the trickiest one, Protect/Destroy 3, you need to tag marked locations across Dire Marsh. In other words, paint some MIDA propaganda to spite Orion.

Your artistic ability aside, tagging the marked locations is one of the most vague and confusing objectives across all of Marathon's early quests, and the in-game hint isn't much help. Below, I'll explain how to complete Protect/Destroy 3...