TMP, take your time on Game Types A-C there isn't a whole lot of rush. Just aim the reticule over the body, get a shot and make sure you don't miss for every 5 downed targets. This will force the Salazar target to show up. If you can get a streak going, you can shoot 5 targets...hit the Salazar target in on hit and keep the streak going with additional targets (thus forcing Salazar to show up again rather quickly).
Another thing that I did was try to get headshots with the TMP on the first 5 targets, guaranteeing 100 points per head (500 total) + 500 from salazar for an easy 1000 points.
It gets frustrating though, trust me...it was pissing me off to no end. Trial and error...it happens eventually.
What do you see, when you look at me? That I'm angry? That I could hurt you? It must be my eyes...creeping along your body, you can feel the death waiting for you in my eyes.