I don’t see really anyone talking about this so I figured I’d make a post about it. I had joycon drift pretty bad almost since I got my switch at launch. I tried using a toothbrush to clean under it, taking the controllers apart, air compressor, etc but nothing worked. However my dad works in computer forensics and suggested I try electrical contact cleaner and it worked nearly instantly. It sprays through a small red straw so I just lifted each flap, and did a few quick sprays of the stuff into the joystick and the drift stopped in just a few seconds.
I don’t see this suggested really anywhere and it’s worked for me for the past few months and it worked on the joycons of 3 friends. Hope this helps!
EDIT: For anyone wondering what varient of cleaner I’ve been using, [here it is](https://i.imgur.com/MHb8yix.jpg) this is one I just had laying around. The comments have also been suggesting a wd40 varients with Amazon links.