Keeping hywin rails clean?

Doesn't need to be complicated just use some foam block which you fasten via bracket or what ever means in front of bearings.
Cut lump out of foam something like the shape of rail just smaller so it conforms to rail shape when forced over rail. The brackets hold it in place.

This just wipes the rail clean of most crap and the bearings own seals deal with the rest.

I was going to say that double seals and scrapers should take care of any issues, along with greasing at regular intervals. I used an industrial Masterwood for about 10 years where the rails were always covered in dust (sometimes buried), and never had any issues.