Let's say if someone was put under a genjutsu to not feel pain by someone with Sharingan abilities. How could that person escape the genjutsu? Even if he knows he is under effect, he still can't feel pain, so would it be possible for him to escape? If not, does it mean that he will stay under genjutsu forever or until the person that used it dies?
the only things you need to break a genjutsu is to know you're under one, and being good enough with your chakra to overcome it's control.
Therefore, it doesn't matter what exactly the Genjutsu does. Kotoamatsukami is strong because it's subtle whereas Tsukuyome is strong because it manipulates time and space. Koto makes point 1 hard (figuring it out, but once you know it's easy, see Gokage summit). Tsukuyome makes point 2 hard (powerful torture effect makes focusing hard). Infinite Tsukuyome does both.
One doesn't necessarily need to feel pain to be free from a genjutsu. All that there is to freeing one is if an external force makes contact with the person that has been caught in the genjutsu or as in the case of the jinchuriki's we see the tailed beasts make them aware its not reality. But in a way kotoamatsukami seems to be different since it even casts without anyone but the user knowing whats been done. So in a way it seems every level of genjutsu and how easy it is to break free from.