Okay for my little tip to contribute here, is that you can use foam blocks of fingernail polish/buffers to give a final polish after you sand down the nub marks, for a smoother finish that resembles more the original texture of the plastic. Those simple and cheap ones that have multiple colored sides, those work great.
Other than that, it's nice to diversify your methods of removing nubs. I have a rough nipper to cut parts off the runner, a single-bladed chinese nipper (much cheaper than a God Hand) to clip off the nub, then I either do the final step with a hobby blade or a DSPIAE glass file, then sand down the surface with sandpaper grits 800-2000. If even after all of that there's still a white stress mark visible on the plastic, you can put on a tiny touch of color with a sharpie or Gundam Marker to hide it.

Also keep some 99% Isopropyl alcohol handy when you go do panel lining, it's good for cleaning out excess ink.

You've probably made this by now, right? 🤨 *I don't have any good tips because I still have noticeable nub marks on my kits, loool

A fine-line sharpie is a great beginner's tool for panel lining! It's a very basic trick to really make a kit pop and a great starting point for going beyond a straight build. They have dedicated paints and markers for this but a fine-line sharpie works. Go over the details engraved into the parts with it, and wipe away excess with some rubbing alcohol on a towel.

Good luck!

Video I recommend : https://www.youtube.com/watch?v=WOmZbU1i90E

Example of panel lining comparison :