Ugh, with the save glitch this was awful to get, but I do have a trick that'll help with the later levels. Basically, combine the Slime Tether with the Slam Dunk trap. This way you can tether the Cultists and other high level ghosts and put them directly in the trap regardless of their remaining HP. This is maybe the only way you can get out of the cemetery with the Grave Monster/multiple cultists and the section before the Keystone Golems.
Also, prepare for a ton of frustration in the Times Square level, as I think they added ghosts from the previous difficulties. I won that by luck and attrition, and it was kind of an ugly stage and nearly resulted in me throwing the controller through the window.