then equip the following: Intervention(primary weapon) Throwing Knife or Desert Eagle(secondary weapon) Overkill(passive skill) Wall Hack or True Stealth(killstreak)
then use the upper way to capture the flag and use upper way again to escape the enemies when you get the flag
NOTE: don't equip melee and smg weapons in this level and use true stealth for capturing the flag and you don't need to kill all enemies just kill all the enemies nearest to you and nearest to the flag that you'll think they'll see you...
