Yeah the guys have nailed it. Baisicalyy you have to set up 2 classes.
1. P90 Akimbo/RPD with One man army and any other perks
2. Riot shield with One man army and any other perks
Once you have done that you need 12 people in a private match and then you pair each of those 12 people up usually by clan tag so one pair would be (A1) and (A2). Then the 1's invite the 2's into private chat and all of the 2's leave. Then the party leader finds a game of search and destroy and the 1's invite the 2's in or the 2's join session.
Once in the game you decide who is riot and who is p90 first. Then you meet up and the one who is p90 shoots a clip into your riot shield. Once you have used up a clip you use One man army to switch to your riot shield/p90 and the other person shoots a clip into his partners riot shield.
When there is 10 seconds to go the person who picked up the bomb plants it and no one diffuses it. This way an extra 45 seconds can be added to boosting. NO ONE KILLS NO ONE STUNS or you will usually get kicked.
Hope this helps