Our business involves manufacturing with textiles so our offices also get pretty dusty.
So i use those green/red scotch scourers, yup like the ones ur wife/gf use cleans pots n pans wif
They are petty cheap and u can cut/squeeze them to size. Depending on how dusty it gets u may need to clean them once a month or so, vacuuming them off works for me, u can also use 2 or more layers if ur paro abt dust.
Using foam, like from ur mobo, will filter dust well, but will also give VERY poor flow 9/10