I've only played with toy pistols (and have repaired them), so do you all have any relevant experience? Including long toy rifles.
"I have limited experience, but I can still offer the following suggestions:

1. WD-40 is almost a universal solution. You can use it to soften and clean dirt off metal surfaces, but try to avoid using it on rubber. In my personal experience, rubber is better suited for silicone oil—WD-40 will cause it to age faster.

2. For trigger jamming in spring-powered guns, you can try disassembling the trigger assembly, polishing the contact surface of the sear with metallographic sandpaper, and applying a small amount of silicone grease to improve smoothness (never approach it with a grinding mindset; that will ruin everything).

3. You need to understand that your abilities are always limited. If you encounter issues like severe tooth damage on gearbox gears or a broken motor shaft (requiring replacement with a professional press), a slide that won’t reset (which may involve complex air circuit faults), a burnt circuit board, or a faulty programmed chip (needing specialized equipment for testing), don’t think you can fix it with the tools you have on hand—just go ahead and buy new parts on Amazon."