Make it a good big piece of glass that you will later cut into many focussing screens for cameras. Take it to a firm that sandblasts things to remove rust and have them sandblast it. Size of the grit determines how coarse it will be. They need to experiment a bit here. There is a huge saving in using this trade secret method of mine.
Many cameras leak light when their foam light seals deteriorate.
A good replacement is foam cut from a computer mouse pad or a scrap of scuba diving suit material. Opening the camera back and spraying both parts of the curtain with silicone spray will usually quiet them. Work the shutter a number of times after applying. In severe cases silicone may be applied to the front of the curtains too. Be careful not to get any on the mirror or the focussing screen.