The easiest CQB is no CQB, so if you want to clear rooms one by one without fear of a close range firefight, get a couple of airsoft hand grenades in your loadout. An airsoft grenade will give you a massive tactical advantage on the battlefield, and your teammates will appreciate it. Always remember to check with the organisers before the game to find out what the rules are for using grenades, and don't forget to pick one up after the game! Happy throwing.