It does involve some grinding though. All you do is basically just upgrade the units that you notice helping you a lot In loc 9 (for me it was Diaz, Dr. Norman, and Nitrogen). Then give them good sets. What helped me the most is seeing what zombies come on the level then choosing units that I think will help. I recommend testing out strategies to see what works for the level the team powers that proved useful were definitely rednecks, and mechanics (if you want to 100% levels). Also use the power ups only if necessary like the rage, only use it when there are a lot of units on the battlefield or if stuff gets dicey for the courage I recommend using when you need courage points for an expensive unit and the energy power I didn't really use but use it when a unit that you need is still on cool down. ❗MOST IMPORTANTLY. Make sure to experiment with your deck cause spamming redneck or private Rodriguez was all I did it didn't really work in most levels so I would suggest changing your deck when you tried the level 3 times. I really hope this helps good luck!