I did a search for the tutorial, but maybe it isn't one.
the scraper was just a piece of rod stock, with a little hook of a cutter formed up on one side of the end of the rod. It cut on the pull stroke. if the scraper isn't aggressive enough, just bend the rod a little to create more side pressure on the hole.
The hook is formed by peening the end of the rod up and filing a cutting edge that cuts on the pull.
I bend the other end at a 90 so I can pull on the rod. Put the bend on the same side as the cutter so you know which side of the hole you're scraping.
Tom