With a narrow time window to complete the sanding (because the Humbrol Maskol has to be removed within three days), I did this task earlier today.
The top case was sanded first with 120 grit sandpaper followed by 320 grit sandpaper. I had some 800 grit sandpaper but I didn’t think this was necessary.
The bottom case was also easily sanded with 120 grit sandpaper followed by 320 grit sandpaper.
The residue of from sticky tape at the back of the case was sanded away.
The bottom of the case looks pretty good.
Defects on the edges of the bottom case were filled with epoxy and sanded.
Overall the case looks good. I expect one or two thin coats of paint will make the surface texture appear more uniform. However, if this does not happen, I’ll give a light sand with 800 grit sandpaper between coats of paint.