If possible, use a nade followed by flash. Rush into the scene and spam at head level on to the whole opponent group while constantly moving left and right in a random fashion. Crosshair movement should be less and body movement should be more. During your movement, try to make a straight line with two or more opponents. In other words, line yourself with the opponents such that two or more opponents are in straight line with your crosshair. That way you will hit two people simultaneously. Empty your magazine. By this time all or most of the opponents should be dead. In case any survive, switch to your eagle. One bullet should be enough for each person as by this time they should have lost most of their hp.
Constant movement is the key with mp5. In this case too, you got to constantly move. But here, you got to move around the target in circles with short random stop/opposite-side movements. The challenge here is to keep the crosshair constantly on the target (preferably at chest level) while constantly moving around him.
For long range, use eagle. You should also use eagle when camping, just keep the crosshair approximately at head level so that when the opponent comes around the corner, his head is in your crosshair and you get a headshot.
Note: MP5's bullets don't effectively go wallthru.
