I tried it on Lost Platoon, difficulty easy, with 2 people to get the, "OVER 200 THOU" achievement for that map. It takes time, but its EXTREMELY easy to do. Utiilize 'hogs when availible, and make sure someone ALWAYS has the laser. It's essential to take out wraiths when the tilt skull is active. On black eye waves, drive the hog with at least a gunner, and shoot em up until your stamina is completely gone, then isolate a few grunts, get out, and beat them down. Then get back in, rinse, and repeat. On bonus rounds, make sure everyone has a chopper, you can EASILY achieve 20k or more, by waiting for the grunts to throw the first round of grenades, then going to town splattering and shooting. All in all, it took me and a good friend about an hour and 20 minutes. But if you want the achievement, with little hassle, this is the way to go.