This video shows step #5, polishing #4 silver. I started this yesterday and thought I had taken a video and only hit the camera button so I restarted it today which is why it looks partially done at the beginning. Unfortunately today while taking the video I broke through in 2 places down to red so I may take all the silver off and re-apply it. I am using a #1,000 stone to polish.
For more on traditional, lacquer based kintsugi see kintugi.com or https://www.kintugi.com/?page_id=225