What DaRock says has some merrit, but I find that most of the time, you will distort the grommet long before the screw meets the Brass insert.

BTW, regarding the screws/washers:

I use screws similar to what Ken shows, but I get them from Du-Bro. They look identical, but the "Washer" part spins freely - like a washer should - but won't come off the screw. I like that. (But they still distort the grommets - Murphy strikes again! )