If you want someone to believe something, make them say it. Literally work to get them to the point they somehow say the words you want them to say to themselves aloud or they repeat what you say back to them. Once someone PHYSICALLY SAYS something more often, they tend to believe that's actually what they believe or think.

Be careful though. This trick can easily be done from yourself to yourself. Literally the "fake it til you make it" idea. Eventually the more YOU start saying an idea or phase, the more it can stick onto you too.

I use this to make people around me to conform to my norms without their knowledge lol. Usually just to see if they will do it.

Example: "Do you think I am an honest person?" "Uhh... yeah."

Later on (weeks later): "I wouldn't lie to you." "Oh, I know."

More time passes: "I know you trust me." "I do."

Later on, that person in conversation with someone else: "Man, she is one of the most honest people I ever met..." For the love of god though, DON'T OVERDO IT. You don't want it obvious like this example (Terrible example, I know) But for some reason, this works like a charm with enough practice.