Scraping used kiln wash off a shelf is not a fun task. I have tried all kinds of tools to make scraping the shelf easier. After trying a half dozen or more tools it comes down to this… a piece of glass. Yes, my favorite tool is a piece of scrap glass. Holding the scrap glass at an angle does a great job as a scraper. When it gets dull and doesn’t work as well I just cut off a small piece so there is a new sharp edge. Give it a try next time.