How do you boost in cod4

Have 1 other person go onto cage match the same exact time as you (You should set it up in advance with someone you know) if you 2 are in the same match than 1 person can pick up a gun THEY ALREADY UNLOCKED and get head shots and within 15 matches if you do it right then you should unlock red tiger for whatever gun you used. Hope this helps worked for me and my friend. :)