Okay I give all you guys out there who have polished a round face lock have my utmost respect. What a pain. Any secrets anybody wants to share to speed this up besides persistence. ...Geo.
I use wet or dry double stick taped to 1/4" plexiglas. 120 or 150 is about a coarse as I ever start out with. After 400-600, if you go that far, 0000 steel wool and chrome polish will take out the marks left by the paper and even out the finish. I seldom do 600 grit unless for color casehardening.
Putting duct tape on wet or dry gives a flexible backing that allows rounded surfaces to be done by pulling a strip back and forth.
If its too rough for paper I file generally.
Power tools often cause extra work on complex surfaces though I do have a 1" wide belt sander I use but it depends on the job. A slight boo-boo with a power tool can take a lot of work or even welding or a new part to fix. So my rule of thumb is hand work unless a lot of metal has to be moved or its a small flat area that is hard to screw up.
I think the HC way to polish in leather belts with abrasive.
Dan