Not sure if there's any easier way at an earlier level in the game, but I found this part where you can obtain both of the achievements.
Load up Chapter 6 "Road to Hell", checkpoint "Broken Highway". As soon as the checkpoint loads, run up past the friendly APC Tank and get behind one of the barriers. You will notice enemies approaching from the north near the bus. Remain in cover until five or more Lutadores get close to you, then turn to the left and pick up the car with the Gravlink. Quickly throw the car at the Lutadores and both achievements will unlock.