(How do you do that? (I'm new) Is there a resource on the forum that explains that kind of work? Looks great!)
As Dave Rase said , round and 3 cornered files .. but I first cone the bore with one of Ed's coning tools which only goes in about 5/8" ... then make it look purty ...
After that a hard scrubbing using a scotch-brite pad on undersized cleaning jag ...
Al