I'm the same. We have to teach ourselves to not offer any information unless directly asked and keep it short and simple. One sentence or one word if possible. Likewise, there needs to be a clear distinction between the I and the we. In other words, you know how you feel and you know what you want. Don't let his demands override your own.

Clear boundaries should be set, within yourself and towards him. In my case, I think about things in this way: some things are his business (i.e. his daughters school performance), while other things are not his business (i.e anything to do with me).

Lastly, I practiced speaking in monotone and "grey rock". It's void of any emotion and the words and topics I am willing to discuss are very businesslike. Think of a cold businessman or lawyer and how they speak, the words they use, and topics you are most likely to hear them speak about. More importantly, what are they more likely to avoid speaking about? Think of of the narc. What topics will never come out their mouths. The answer to these things, the thing you want to avoid, is talking about yourself. Letting who you are or how you feel come out into conversation is dangerous. It can be used against you by manipulation or through turning the tables on you.

We are supposed to be forthcoming with people but not with a dark triad. We are open with others because it builds connection, closeness, and trust but, this is the very thing you are trying to avoid with the narc. Man, I wish I knew this years ago. I wish I was proficient at it today. He catches me off guard though and I react with absolute honesty. It's very frustrating to say the least.