Start a Terrorist Hunt game with "Lone Wolf" off. Set the difficulty to Realistic, and use the Killhouse map. Set the amount of enemies to low-medium, then start the game. Make sure to bring C4 for the Assault points. At the start of the map, run up the stairs, and place your teammates at the top of the first flight of stairs. Immediately use the right side of the wall as cover. You should be able to see a rappel rope on the left side of the wall. Next, do one of the following things to get A.C.E.S. points in the indicated category:

Assault:
While still in cover, throw a C4 out so it lands at the bottom of the rope. Wait until someone starts to climb down, and halfway down, detonate the charge. This will get you +3 Assault points for each kill. Once you run out of C4, use explosives.

CQB:
Just blindfire the enemies rappelling down the rope. Each kill in blindfire gets you +3 CQB points. Alternatively, wait until the enemies reach the bottom of the stairs and start to move towards you. After they are relatively close, pop out from the cover and kill them. This will get you +3 CQB points.

Marksman:
Simply shoot the enemies as they are climbing down. A light machine gun is recommended as they rappel down quite often. Each kill while they are still on the rope gets you +3 Marksman points.