I used this strategy sitting near the double tap machine to get to round 41 on solo mob of the dead. I never open the 1500 door that goes to the wardens office unless I go down and have no choice to escape. I did eventually down and have no choice but to open the door. I mostly just spammed the paped acid gat and got a max ammo almost every single round somehow. I did eventually go upgrade the retriever on round 30 something which was a horrible idea and took a long time but not to bad.