First of all, I've never hacked and never will. I've been playing this game almost daily for about 2 years now and in that time I've managed to create my own technique and perfection it. First I jump and locate all the possible targets that I can get a clear shot on. When I fall down, behind the wall, I try to aim in the player's general direction so that when I jump my crosshair points at him (this is probably the "tracking" that you taught I was doing). When I jump again I try to correct my aim midair in order to get a headshot while still paying attention to the location of the other players. I repeat this process until I've killed my first target and then go straight for the next one (which, as you said, is the closest one to my target). The constant spamming of crouch and jump allows me to do this fast enough to get kill after kill in a rapid succession. Because I do this often I got kinda good at it to a point where most of my kills take one or two shots, but sometimes this can take me anywhere between five to eight shots or even more, meaning that I have to spam the shoot button until i get lucky enough to shoot him. This might look like aimbot to some people but please trust me when I say that I wasn't aimbotting.
I'm sorry for any grammatical mistakes.