On the first level on RSV2 you need to pick your regular guns and C4s+Frags (this fun hint could be CQB help you can do any time a fire extinguisher is near or across from a door in the hall way).

OK so you are going to have to make sure that you snake cam the room and target enemies, make sure you have your team on infiltrate mode (NOT assault mode).

Place the C4 on the fire extinguisher, put your team on follow orders, open the door to the room the enemies are in and run to a safe distance with your team and detonate.

Then turn on your heat vision and fire, or just fire through the smoke at the targets on the enemies heads.

This is a way to be untraceable at killing your enemies.