Precisely what Chief said. I used lots of high sulfur cutting oil (as you can see), only turned clockwise with the bit, went slow and removed as many chips as possible every 3-4 full turns of the reamer.

A few more words.

Make sure to have a good way to clamp the cylinder without marring it. I used poly inserts on my vice and they worked well.

Make sure you get a GOOD handle for the reamer. Buy once, cry once. I recommend the Brownells handle you see in the pics.

Make sure you use dykem around the charging holes to see when your reamer touches down on the chamber recess. Cleans up with acetone.

A few pics to see the finished product...