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.