This achievement is quite easy, it just takes time. It's easiest on the map Killhouse and having a couple friends help out will make it a cakewalk.
Two people is enough, although the more the better. Always communicate with your team! Have one sniper go up to the catwalk to pick of enemies and distract the enemy team. If you are more than three having another guard the sniper from flankers is usefull but this is not necessary. If you can spare a man, mostly if you are 5-6 people on your team, have one guy go under the catwalk and flank for additional distraction and another go to the roof for overwatch and sniping.
The leader (You) and the rest of your team can choose between two routes, either through the house and then left/right. There you can also link up the man going under the catwalk. Or you can go opposite to the stairs and then just go straight ahead for the back of the enemy base and up the stairs for the exfil point.
There is yet another strategy, which is really easy. Have the leader camp at the spawn point with one or two guards, while the rest of the team clear out the enemy team.
-Make sure to always cover the leader, he is your key to respawns! Teammates should always sacrifise themselves to save the leader.
-The leader can see the location of the enemy leader, use this to your advantage.
-If the leader kills someone, he will not be able to respawn. If you flank an enemy, and he hasn't noticed you always let the leader kill him.
-Use cover in every firefight!
-Sprinting is very useful.
-Grenades is your friend. When you reach the opposite house, always throw a grenade or two. You might get lucky.