On CQB, take a frag grenade and C4 as your gadgets. With your other weapons you should have an assault rifle. When you set it up, make sure your teammates are in the game, at high enemy level, and it is on normal. When you start, tell your teammates to go to the box in front of you. Then, go to the corner to your right and take cover on that wall. Throw a grenade down at the other end of the building. You should get one or two kills. Wait for another terrorist to appear, then throw the other grenade. You should get three or four kills. Walk out the door to your left then take out your C4. Throw it inside the door to the brick building. Shoot the upper left green box in the brick building. Wait until some terrorists get close to the door. Detonate the C4 and keep doing this until the terrorists stop appearing. Go to the end of the brick and throw a grenade through the doorway. You should get a few more kills.
Choose single-player Terrorist Hunt. Make sure you have C4 on you. Choose the Presidio map. Set it to the Realistic difficulty and high density. Make it that so you are a lone wolf. Once done, launch the game. When you start, go forward in the direction you are facing. Make sure to sprint to get there quickly. After sprinting you should see a set of doors. Take cover next to the closest one. After you are in cover, open the door. At the far end of the room there will be a man that will walk by. Kill him by precision aiming (firing from cover). On the left should be another set of doors. Throw a C4 in front of it, but not on it. Wait for one of the doors to open and detonate it. Then throw in another C4 and detonate it. The most you should get is six kills, but it may be lower though. Repeat this to get a lot of Assault points.