FWIW, dust can have sources other than the factory.
After using my old 9800 for a few years, I found myself increasingly cursing those sloppy, dust filled factories! Then I opened the plastic cover and noted that a large amount of dust had accumulated inside the cover where it could easily transfer to the media, especially when loading rolls. An occasional wipe with a slightly moist towel cured my dust problems for good, no brush needed.
Of course with sheets there is the problem of loose chips breaking off from the edges and migrating on to the surface. For that you need a brush or a
bulb air blower, and careful handling will also help.
It's very easy to see if you've got a dusty sheet by viewing it in grazing light across the surface. I have a few foot operated, table height lights in the shop specifically for detecting dust. Not a big fan of Swiffers, I find they tend to deposit lint along the edges of media and mounting boards and create dust bunnies in the shop that find their way on to exposed adhesive surfaces.
The curse of boxed sheets is dust, the curse of rolls is curl.