I've always had a hard time trying to find a good nail file. Most of the ones I have tried, even those expensive ones with "diamond" dust as the abrasive portion, have worn out, bent, broke, or just plain didn't do the job. The Tweezerman Nail file is the best one I have ever used, and one of the best priced... and you get a nail buffer, too! If you follow the directions that come with this file, you will find that you'll have no more scraggly bits of rough fingernail left after a filing session.
I experimented with the buffer, too. I usually wear polish, but I wanted to see what this thing would do. Was I ever surprised! My nails were as shiny as if I had polished them with clear nail polish! This is one iy=tem I want within close reach at all times! i keep one in the glove compartment of my car, one on my nightstand, one in the bathroom, and one in my desk drawer. At this price, I can afford to have one in every room! I LOVE THIS FILE!