Kalphites again! I usually set up my cannon in the soldier room and try and blast my way through this task as quickly as possible. However, I am finding it hard to find high population worlds that are empty to use. Should I just set up in the worker room instead to get it over with? Or stick with the soldiers on a lower population world. Or something else?

I just got to a low-ish populated world.

I just kill the level 28 ones, as you can afk it.

 

Just click back to the screen every 30 seconds or so, click "attack" on every worker (its multi so they all attack you)

 

 

 

Easy.