How do I make a mounted entity play an animation on a keybind?

I'm trying to make a Titanfall mod for Forge 1.20.1, and I'm currently working on the reload animation for the Titan's weapon. I've animated it, but I need to figure out how to call the animation if I press R while piloting the Titan. 

Also, unrelated, but if someone could tell me how to get two separate animations to play at the same time (Say, reloading and walking) that would help a lot.