I noticed while playing that if you try to complete the level with very little progress, the game will show you the end screen with percentage of completion for the 3 categories, evidence found and bodies found, and allow you to go back to the level rather than let you finish the level.

This is very helpful for the true cleaner levels where you don't have any completion indicators for trash, furniture, blood and evidence while playing the levels. So my tactic here is to pile all bodies and garbage bags up BESIDE the disposal area/truck, so they are conveniently there but haven't been tossed in yet and therefore won't count towards completion percentage. Then go ahead and clean, put back furniture, pick up trash and evidence. Once you believe you have done all you can, DON'T touch the trash bags and bodies, go ahead and complete the level, it should show you the percentage of completion for all 3 categories, and which evidence you are still missing. Because you've not disposed of any of the bodies the game won't let you complete the level. So you can keep doing this until everything aside from the bodies found are all at 100%, then dispose of the bodies and trash bags, and you will be able to complete any true cleaner level without much headache.

As an added side note, during true cleaner levels don't use the ozonator in the beginning, this way you can use it as a visual indicator for the last bit of blood you are hunting on a level.

Happy cleaning everyone!~