below is the easiest way we found to boost this achievement.
1. you need 6 unique gamers in the room
2. load up the map import/export
3. the person getting the achievement will run a lap around the map, getting both hostages to follow them at the same time.
3(a). if the person getting the hostages removes all armor, and switches to the pistol before running the map, they will move much faster and each game will only take around 90 seconds
4. go get the hostage who is farthest away first, then come back to the closer one
5. at the same time you can work on other achievements
+ those not getting the hostages can work on weapon achievements
+ you can also work toward your 500 and 1000 kills
+ those getting the hostages can also host each match they win and they will get the achievement for winning 10 matches they have hosted
+ as long as it's at least 3 on 3 you can get the cluster bomb for blowing up 3 enemies with one explosion