tab; always be curt, serious, brief, being brief is the key,
answers what you have to, then turn your attention elsewhere as if you have somewhere to be, s/t to do. Don’t linger, will give him the wrong message.
Although MidPath makes a good point. and I’d take his advice. It’s important to note sometimes guys take this, telling them nicely you wish to have a professional etc.. as a message that they have to work harder to get your attention win you over , and this could lead to you changing your mind when they win you over.
However showing that your totally not interested physically giving him a curt not interested vibe that gets the message across way better. Don’t be rude, just act totally not interested.