You are probably quite correct and Fixcinater's sanding is also not a good idea. However, if you are not precious about prints (only reproductions from negs) then it's not a big problem and the dust will settle.
i'd hang it from a piece of rope OUTSIDE
and paint it there ...
i wouldn't do that in a darkroom
unless you have made a spray-tent
besides, you'll be huffin' fumes
i don't do anything besides photo stuff in my DR.
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artwork often times sold for charity
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