Scotch Brite is a good coarse filter material. Be sure and get the "sanding" type and not the type with soap. It typically comes in three types. Coarse, Medium, and Fine.
Dollar store scrubby pads are widely used in sump systems and canister filters.
If you are using a lot of filter floss, and the polyester quilt batting isn't cheap enough, find the nearest commercial or wholesale air filter supplier. They will have, or can order a couple of different weights of filter with no additives. The manager of my local supplier gave me a piece about 12" x 36" to try. This one is stiffer than the blue and white filter sheets and stiffer than quilt batting, but it is very good at trapping particulates.
And, by the way, they will also have furnace panels available that are incredibly efficient and quite reasonably priced. I buy a three layer panel what has a latex additive to one layer. A 20" x 25" panel costs just over $6.00 US. You change them two to three times a year. Far, far more efficient than the best 3M allergy filter panel.