OK I'll stick my neck out here. If its really a sharp edge file it, tap it w/ a hammar. Whatever ,make it unsharpe to insure that the fabric will slide over the protrusion during shrinking, does not tear or hang up. But rounded edge like a rivet or screw is just as well left quite alone until you get into nitrate or Polybrush. At that point if you think it might suffer fabric abrasian, put a very small fabric patch over it. It is most important that while wet sanding to avoid all of those raised areas or rivets in the covering. Don't injure the fabric over the pointy places as it will never heal with dope. As I recall this is contrary to 41.13 as well as Stits and Randolph instructions though.