Help them to hear for themselves. Spend less energy explaining them what they should believe and why they should believe it and why they should disbelieve all the other alternatives, and spend more energy simply trying to help them learn how to listen to the Divine.
And remember that the Divine speaks in so many varied and unpredictable ways. Don’t expect communication to come to someone else the same way that it came to you. That person you really wish would believe? The Divine is already speaking to them, and probably in a really unique way. In some special way that will catch their attention and reach the depths of their being. They may just need a little support in learning how to listen with spiritual ears.
Yes, some will believe because of what you tell them, and that’s good as far as it goes. But faith built on someone else’s faith will only last so long. Drinking from someone else’s fountain will only end up leaving you thirsty. Eventually everyone needs to find their own faith welling up within themselves.
So just help someone quiet down and listen. Which means that you probably ought to be the first one to quiet down and listen.