This is basically a small but important addendum to DirtyGlasshoop's method.
>maximum people 6
>minimum is however many you have any in the session
>point limit is 10,000
5 people is recommended because if you have 4 and one person has to go, you're screwed.
The main change is instead of switching off, one person gets all 10,000 points alone. With 4-5 people this takes roughly 8-9 minutes (if it takes longer than 10 minutes, someone isn't trying).
But why have one person do it? Because the host gets 2 kills added towards their achievement for every 1 kill. (thanks to Redemption626 for this revelation).
10,000 points for one person is about 80-90 kills a match, which equals out to 160-180 every 9 minutes. That means it takes less than 2 hours per person to get 2000 kills. If you doubt this, look at your lowest bar, do one of these sessions and look at how much it goes up. I got 250 pistol kills and about 400 rifle kills in 3 9-minute rounds.