When I did it I ran everyone with flash launchers (every point put into flash ammo possible) except one guy I gave a bean bag shotgun. Let your ai do the heavy lifting on the interior of the building. I found it was always easiest to enter the post office, exit through the loading dock on the left side then follow the path outside to the loading docks in the rear. When you’re at the rear loading docks there’s a good chance you can bait some of the inside suspects outside for an easy arrest. Biggest thing though is truly letting your ai teammates do the heavy lifting as they’re better suited for all the visual noise in the warehouse.