Here’s one of my favorites: the humble micro-mesh stick. I use these mostly to smooth (or un-smooth) nibs, but also to do minor nib work. You can use them over and over; the abrasive lasts for a good long time.
My stick is made of a cushioned foam with micro-mesh in different grits applied on both of the flat sides. Mine has three different grits. The two coarsest share one side: those are colored dark gray and white. The dark gray is either 1500 or 2400 micro-mesh (I’ve seen both measurements used). That is the coarsest, and I use it the least. The white is 4500, and therefore smoother than the gray, but still coarse.
The light gray, on the other side, is 12000, and that is the smoothest. I use the light gray side the most.
You can also find micro-mesh in sets — of either sticks that are one solid color (with one grit level) or small squares. I prefer my three-section stick because it’s more convenient for me to have everything in one tool. Others might like the separate sticks or squares.
If you want to try using these, and are new at it, just make sure to read up or watch videos on nib smoothing and nib work before doing anything. Then practice with inexpensive pens until you feel confident that you know what you are doing and won’t inadvertently damage a nib you care about. Make sure the nib tines are aligned. Work on your pen when it is at least partially filled with ink: try a few strokes on the micro-mesh, then write on paper to see if that was enough; repeat if necessary. Always remember to go lightly: you can go too far with these sticks or any abrasive.
I got my micro-mesh sticks originally from Richard Binder, but he no longer sells pen repair products. You still can buy them from just about any online seller of pen repair equipment, and many online pen stores. You can also buy them outside the fountain pen world: from hobby shops, woodworking supply stores or beauty supply shops. If you are online, search for “micro-mesh stick” or “nail buffer,” and you’ll find them.