Choose the first Dead Man Walking level. You will start behind a van. When you just enter the level, quickly get the painkillers and go behind the van where you started. Use your camera with intelligence to see when the enemy is coming. Quickly enter slow motion and kill him with a quick weapon. Then, repeat the procedure. When they die, go in bullet time and get the weapon. When the enemy number starts growing, use your grenades and Molotovs. Note: Bullet time, and not shootdodging, is very essential to stay alive in the first place. Use it wisely.
