I use fine and tiny. The file is about 1/4" wide. Some tape a protective piece around the pin. I just file with my finger against the file. With a little preasure towards my finger i dont slip. Anymore.
I think they are 6 inches long. Came in a set of six different shapes/points. The set came with a handle.
Another way is to put a few layers of masking tape over the pin. File right through the tape for the pin but it will save you on the scales if you slip. Once.