Your specific question is for resources to improve, but there's no royal road to soldering, or geometry, or going to the gym. The fastest way to make progress

Your specific question is for resources to improve, but there's no royal road to soldering, or geometry, or going to the gym. The fastest way to make progress is to practice, there is no pill or wiki or video that makes progress faster; if anything those make progress slower. Soldering is exactly like the gym where attempting to avoid time and sweat invariably results in slower progress than just doing it. Especially if someone is selling something to make it easier, it won't work. If you've already started as per the post you've likely exceeded the skill level covered by "how to solder electronics.pdf" by the Heathkit company or similar intro level stuff. The only specific technique I can think of is debugging your own boards. Debugging time is very motivational for avoiding mistakes. You'll find it harder to learn to solder if you repair stuff, easy if you build a kit or two of similar complexity to what you're trying to repair. You'll learn anyway as long as you put in the time and sweat it'll just be more emotionally motivating if you're repairing your own work than repairing someone elses.