Hi Bryan, consider both hands intact, as with the other comments, there is always a sandable finish off any tool, resharpen at best, shear cut for fine finishing cuts, like wise should you sand to a ultra smooth surface, will it be of benefit as you've said, not if it's pine to be painted, then most would say to stain or paint a piece, any marks will show.
A question I ask at a demo once on finishing, what grade are some of the buffing compounds, would some be coarser than the already sanded finish, there was not a real reply or moving along .. as embarrassment it was not known, but some polishes can be found to be abrasive.
Then hand, Power or to include rotary sanding, it's a case of time, this is the benefit to both the last options, as are using fresh adbrasive, worn out never works, 240 never makes 120 ..
Pens .. if it comes to a finish are the exception, when you find many using grades going into the thousandths.
I've "J" cloth, first real breakthrough, an since micromesh and velcro discs' and somewhere besides, I do have what is classed as medium and fine in green sandpaper 1/2 sheet rolls .. have I taken to use it ..
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Cheers David