aris357 -- Thanks
If the pin hole has to be changed (& all of mine have) I locate it early on in the fitting process, see below.
To take off large or heavy areas I use my bench grinder. Depending on how rough the grinding, you may see fine chipping beyond the actual grind surface. Getting closer to the desired surface, change to a finer abrasive. First, usually the bench grinder, then as I get closer to finish I either use a file or an abrasive in my Foredom setup (a flex shaft outfit with a motor & foot treadle for speeds). My tooling uses little abrasive sleeves in various grits I use as it gets close to finish.
I have found pearl to be a pretty tough material with only issue its brittleness. Anything tending to strain it (as in not flat against the frame or pin hole distance against the frame) hazards a break. Finishing starts with maybe 400 wet or dry paper, then finer, with final finish a rag buff.
The pin hole I consider a hazard area. To locate the hole for the pin in the frame I punch out the pin, clamp the pearl in its proper place and start the hole by drilling thru the frame hole. Then take the pearl off & drill the hole a bit larger than a close fit to the pin. Be sure to drill deep enough that the pin doesn't bottom in the hole. If the hole is too big or off a bit, I wax the frame, the pin, & fill the hole with epoxy & assemble it in its desired position. When it is set up, you will have a proper fit. You may have to heat the frame some to free it the first time. Be sure to do only one pearl panel at a time.
Hope this helps. I tried to explain what works for me. You may figure out something better.