There is a jig that you use to locate the hole. The rest is by hand for me, in fact, I let a machinest locate the hole for me as the difference in settling and perfection is measured in the thousandths. I send the jig and MSH out to have the hole done to insure the MSH is what is matched up to the frame holes properly, then the rest is done with my trusty files and hands. Now, this insures that even if the manufacturer of the frame didn't get their holes right, I didn't compund the error. The fellows I 'commission' to do this for me are more demanding than anyone I know and deliver absolute perfection for me to begin my work on, and they understand the 1911 and the end user.
Remember, you commission artists, anyone can hire any bubba off of the streets if they are willing to settle.
Now, how good do you want your's done is up to you. You have a mill and are good, this should be a cake walk. You may even be able to do it off of the measurements alone.