I've used a Dremel Tool for decades. There are some "tricks of the trade," of course.

Couldn't you just use an ordinary emery board available at any place that sells cosmetics?

Another option might be to make you own. Use something like a large Popsicle stick or a piece of wood in that general shape. Then glue ordinary sandpaper to it (or use adhesive backed sandpaper).

Go to Sally Beauty Supply and look through their assortment of nail files. Files don't work on my dog's nails, they don't really do anything. I use the Dremell on her. But if the glass nail file works on her, I'd see if they sell them for cheap at Sally's.

I did use a glass nail file from Sally's. It was $3-4 IIRC. I was worried that it would last for only 4 uses. I want something that won't wear down. I thought maybe some tool that files metal?

She would run from a dremell. My other dog has been trained for pedipaws (which is like a dremell), but my little girl dog freaks out when I turn it on. I'm lucky she handles the manual nail clipper (which my other dog would not tolerate).

What about a metal file, not the type meant for human nails but the type one can buy at a hardware store?