Cindy is pretty easy to deal with considering all you have to do is close the door when you hear the sounds of her wings flapping and then open the door when you think she is gone.
As for the others, the RNG can be pretty random and very difficult. Sometimes it is hard to get to the vent in time or not knowing of someone being in the vent until it is too late considering that it is very hard to differentiate between the footsteps Mina makes when going out the doors and the sound of either Crystal or Emily in the vent intermingle with one another (as in the sound of Mina’s footsteps is pretty loud and sometimes the vent movement is a little quiet at times as you’re busy with another task).