@StripeyChina As much as I hate meds, I can see that others do need them, and it certainly sounds like your friend really does. As you say, I don't know what you can do to encourage him to take them.
I definitely think that listening is really helpful if you can cope with it. But letting it go on too long can make people more worked up and more convinced (if that is possible). I don't listen when people tell me I am talking nonsense, and it can either make me really annoyed or even make me laugh, depending who it is, how they say it, and how I feel at the time. I desperately want someone to tell me that I am wrong and it is not really happening, but when they do I think that they are not listening or believing me, and that they have been fooled by the devil. So you can't win really.
I don't know about mania as I have never experienced this, but it could be that the talking lots is part of that. I know that for me I won't talk about my fears with anyone when I am getting ill. Until I am really unwell and then I will be really open and tell every health professional who asks any vague question. It gets to the point that I am terrified and can't think about anything else so I can't talk about anything else. Can't gather my thoughts enough to distract people's attention away from me by talking about something different as I can in the early times of a psychotic episode.
What helps me when I am extremely psychotic is being talked to like a child. Because I am like a terrified child. Having my focus redirected. When people say "focus on me Fermat" and get down to my level (I am normally curled up in the corner on the floor). When they talk to me about normal things, especially if they don't expect a response. Recently when I was on a 1:1 in hospital, one nurse spent hours just talking at me about her life, and it was so helpful. She would occasionally stop and redirect me to focus on her, but apart from that she told me stories about her life and her dog and stuff. That's generally better than getting into a debate which you will lose because your friend will have spent hours and hours thinking about their delusional beliefs, and rationalising them. And even if your argument is better, they will just ignore you anyway.
Hope that helps, feel free to keep asking although I am going to bed now! Got an early lecture!