Jerry, unfortunately, the only way to remove the remaining backing (and old glue) is to scrape by hand. Suggest that you try the Red Devil wallpaper scraper. It allows you to change blades and to get the floor ready for new vinyl, you must have an extremely sharp scraper. One word of caution from someone who has worn blisters upon blisters on my hand removing vinyl flooring. Take a 2x2 and cut a 3-4 inch piece off. Drill a hole (not all the way through) that is the same diameter as the handle of the red devil tool. Then put the 2x2 on the handle. This way, you are scraping with your whole palm and not just a quarter size area right smack dab in the middle of your palm.