Sometimes the chemicals you use to remove another chemical is worst that the one you are removing, some of them have low flash points and it only take the water heater or furnis to ignight the fumes of a chemical. I am in the flooring industry and we scrape the floors with stand up scrapers, you can rent a 8 inch razor scraper from your local rental shop. It should not take to long to scrape. But these are just my thoughts. I know someone who was burned badly is the same type situation.