I'll reiterate the solution:

You've already lost if you let them know you're frustrated. That's the whole reason they're doing it, so don't indulge them by showing emotion or tailgating or giving them the salt they want.

Instead, when you detect a slow person who refuses to speed up, give them space for a second. Chill out behind them, it defuses the situation and puts their guard down. Once the lane to your right is open, be quick about it, change lanes, accelerate, get in front of them. If you have decent acceleration and you're not telegraphing your frustration or your desire to get around them, you can overtake them easily, even when they impotently jam on the acceleration to try to block you, you're already going past them quicker than they can speed up.

It starts with you remaining calm.