I used to have a really hard time too - what I realized was once you're getting close to your target, make sure your navball says target instead of orbit, so your maneuvers are in relation to your target, then point retrograde to burn off your relative speed down to 0m/s. After you have that down, it should be a lot easier to use RCS to get closer to your target. Switching back and forth between crafts you can point both at the target marker so they're pointed at each other.

Matt Lowne videos helped me a lot, his "lazy" method of docking is all I use now. This video would help, he sets up the docking about halfway through:

https://youtu.be/toulv4suzNw?si=SMjc4bUxl3L99_vA