You say confined space? in which to work,
dry sanding and cutting IS a health /lung risk.
youll need to use a proper cuff type micron dust filter respirator,
or install proper vacumn dust extraction.
Otherwise you will pay dearly with your health.
Do this properly!!

Yes, I hear you. I only use a paper painter's mask. Since I do this
only a day or two a month, I figure I won't kill myself, but I would
like to reduce the dust.

You need a vibrating tumbler.
That's an idea, but I'm not sure I want to polish the threads.
Wrapping/plugging them before tumbling would likely cancel out the
labor savings of tumbling, and I still have to do a lot of shaping
before the parts could go into the tumbler!