They r easier to do solo, & once U get 29 , U can save out & goto Data Hive. If U do it Co-op U have to go thru the entire campaign. It took me alot of heartache to find this out. Also solo U can take ur time & save & quit comeback another day & keep going until 29. If the guard doesn't follow U down it's really frustrating. Lastly use map from achievement hunters website.