I find covering the Artex with wallpaper paste and leaving it for about 10 mins does the trick. You will still need to use a sharp scrapper but it's a lot easier!
there is a product now available callled x-tex you apply it like paint leave to dry then scrape off the artex with a wallpaper stipper,i have only seen it available online and it costs about �20 for 2.5 liters.