This achievement will probably come naturally while playing the game. You have to play trough the game at least twice for all achievements to unlock.
If you want to boost this than load up the level FRONTLINE. Start by killing the guys in the rail car and pick up an assault rifle if you don't already have one. Now switch to MGR to burn trough the enemies. You can reload checkpoint or keep going trough the level as you wish, reloading checkpoint does not reset your progress towards this achievement.