I just used some 200 grit paper and I made myself a jig from an old AE shock assembly tool. Cut the end of it off so it does not protrude through the bushing. This allows me to hold it in place and apply the pressure properly.
Use your calipers to check your progress and you will be fine. After you sneak up on the first couple you do, you will get a feel for it. You don't have to be exact. It is the principle of getting it to free up that makes the difference.

Take your time and I promise it will be worth it in the end.
Regards,
TEX