Even when you think the other person is a techie, I've seen it generally helps to assume that he is not, to avoid this Curse of knowledge.

Also at least in my domain, I've found analogies are a great way to explain super complicated things very easily.

Old world physical analogies work great (like a bank, wallmart, etc) but analogies using other startups, i.e. we're the Uber of X, or we're the blablacar for Y not so much. Because sometimes the other person may not know what blablacar is (or for that matter Uber).