Two players are recommended for this trick. Before you breach the wall, grab a Striker and an AA-12. Once you breach, run to one of the sides with the AA-12. Keep running while killing enemies with one shot. Once you get to the part with the Riot shields, switch to the Striker and rn towards the shielders while firing. Almost every time when you use two players, one person will get to the hole and the other will either get to the exit or go to bleed out. If you bleed out, crawl past the enemies. You can't die and have about two minutes to drop to the bottom.