I started with the idea to make Washable Swiffer Duster Covers from fleece, but I didn't want to cut all of those layers before sewing.
I started with a quarter yard of fleece, 9 inches by 60 inches. I had already used some in whatever project inspired me to buy it in the first place. I took what was left, and cut it in half long-ways. I looked at the length of the prongs on my Swiffer Duster, and started with accordion folds on the fleece, so 4-1/2-inches wide by back and forth folds. I tweaked it a few times to get the folds to work out (no partial lengths).
Next I realized that my sewing machine was NOT going to sew through all of those layers. In fact, it complained loudly just sewing through two layers of fleece (and this is supposed to be a quilting machine? really?), so I made as few seams as possible. I sewed two channels for the two prongs in the middle fold. Remember that the middle line of stitching doesn't necessarily go all the way to the end; check your duster on your fabric to see where to stitch and where not to stitch. I also put in a few stitches at each fold.
Since my sewing machine wasn't going to add as much to this project as I had planned, I needed another idea. (This is where flannel is better.) I took a detour through nylon snaps (this fleece was too thick for the snap prongs I had), but then I was holding the sharp awl from my snap kit for the next idea! With the awl, I worked a hole through all of the layers of fleece. I threaded some coordinating yarn through a large needle designed for yarn. I tied off the top all together, the bottoms on either side of where the prongs insert, and two holes in the middle to hold the middle layers together.
So finally, on to the last step! I cut half-inch-wide strips along the sides. I asked my boys if they wanted to use their scissors, but they wanted to snuggle and watch instead. Once the duster was done, Cale wanted to put it on, and then started dusting everywhere I pointed him. (Hurrah!) There's a lot of pollen on my brand new duster, but that's OK: it's washable and the pollen isn't covering everything now.
If your duster needs enhancement, a very light mist of mineral oil will probably help.