Scotch Brite pads will do nothing....you need a flex hone. 400 grit. You get them here: Rifle Brushes, Flex Hone, Gun Brushes
You can use their honing oil or Mobil 1 or similar....
I never had the firing pin hole issue.....I'm guessing you need to chamfer the hole itself, but I have no idea how much or the proper process. There should be threads here on the site to tell you how.
Sorry to hear about your experience with your XCR-L.....unfortunately, I had the same problems and it took a good 9+ months to get it sorted. Looking back, it was worth the trouble, but I understand your frustration.