You don't need any real educational resources to get good at soldering. Any random primer will do. It's genuinely a simple task that doesn't require a lot of explanation or have a lot of tricks.
What gets you good at soldering is just practice. Solder a lot. A fun and easy way to do this is to pick up those cheap ($5 or less) electronic solder-it-yourself kits and do a bunch of them. Include ones that contain small surface mount parts.
You can also practice desoldering on them, or pick up broken electronics and desolder parts from those.
> managed to desolder and resolder a stick but the controller doesn't turn on anymore.
There's a chance to practice repair (which is a completely different topic from soldering)! Odds are very high the problem is that you've made an unwanted solder bridge or you have a cold solder joint.
What gets you good at soldering is just practice. Solder a lot. A fun and easy way to do this is to pick up those cheap ($5 or less) electronic solder-it-yourself kits and do a bunch of them. Include ones that contain small surface mount parts.
You can also practice desoldering on them, or pick up broken electronics and desolder parts from those.
> managed to desolder and resolder a stick but the controller doesn't turn on anymore.
There's a chance to practice repair (which is a completely different topic from soldering)! Odds are very high the problem is that you've made an unwanted solder bridge or you have a cold solder joint.