This way isn't the best, but me and my friend do this all the time, and you gain a lot of experience points. You can do it with anywhere from 2-12 players. Everyone needs a class with Riot Shield and One Man Army, and a class with RPD (Suppresser helps with smaller groups). When you are all set up, one group heads into a Search & Destroy lobby. You'll want to try to start your own lobby instead of joining one. When you get in, invite the other group or your partner to the game. Have a partner chosen on the other team that you'll boost with. Also have a spot on the map chosen to meet. You and your partner will meet in this point, one with the RPD, the other with the Riot Shield. The one with the RPD will shoot their entire clip into the Riot Shield, then both will use One Man Army, player with Riot Shield goes to RPD, RPD to Riot Shield, then shoot your entire the entire mag into the Riot Shield, and repeat this process as much as you can. Enjoy!