Go to Multiplayer.
Play Online .
3rd person cage match.
Invite your friend as quickly as possible.
Tell your friend to stay in the message area to get the invite and join quickly (You may have to do this a couple of times). If cant do it or cba then just tell the other person to join session.
When you and your friend is in the same game, just play in turns e.g. you kill the other guy 20 times then he does and so on.
*Hints and tips*
1.While the game is loading try and make a few classes with different weapons which you usually dont use, they get you more points.
2.To talk easier through the game have a chat thing open.
3.If youre killing the other guy tell them to have the tactical insertion to kill quicker.
If you dont understand something or if youre stuck feel free to leave your psn and Ill try to help you tomorrow.
If you already know this no need to go mad about it, im just trying to help.
In like 1hr i got from level 40 to 44