I am wondering what type of bit is generally used in a rotary tool/flex shaft to sign the mpc with initials/logo and the mpc specs at the end of a job. Is it a very small ball point tip? If not, which one do you normally use? I have seen this done before but am not familiar with the bit type... I have a very fine pointed cone shape metal bit but that actually doesn't work very well... Thinking a very small diamond ball point or something (I've seen these really cheap at Harbor Freight and such) might fit the bill? Thanks!