I used the same thing I use to do eyes. I keep several drill bits on my desk that have a flat end on the other end from the drill bit part. I made them with a drill bit flat end. When doing eyes I try to use one about half the size that I use for the back ground color in the eye for making the black.
Some drill bits have a rounded end and they are not good for this.
Hey and no Guido coming, LOL!