Here's a good technique for acquiring some easy PP. When the Special Forces are in the mall, run to the grocery store, bringing along some guns. When you enter the store, immediately head towards the pharmacy. Open the door to the pharmacy, head on inside, and shut the door behind you. Shoot out all of the windows in the pharmacy and wait. Eventually, the Special Forces soldiers will come looking for you, but they will all gather around the door. They are sitting ducks for you here. They won't fire back or run away. Clear this group, leave the pharmacy, then walk back in to repeat.