Trial And Error:
Could you give more examples to unsatisfactoriness that are less obvious?
I have more trouble with this than the other Cs.
Sure. Like I said in my last comment to you, I experienced intense needle-like sensations that were very unpleasant. Intense itching, and getting hot during meditation which was unpleasant. The emotional and mental states such as fear, doubt, and angst were all unpleasant.
Sometimes I felt myself grasping at sensations with awareness in a way that felt jarring. I think Daniel has described something similar in his practice, as "feeling out of phase with objects" or something like that.
There's no super secret magick trick to discerning the 3Cs. It's all right there in your experience. You might be over-thinking things and expecting the 3Cs to be way more profound than they actually are. The 3Cs are extremely ordinary, it's just a matter of teaching yourself to experience reality through the lens of them.
Also, the 3Cs are all linked to each other. For example, I had attachment to self-image. Thus recognizing aspects of my identity and attachment to it, as not-self, was difficult/jarring/unsatisfactory.