A sharp razor blade scraper is what I have always used on any gasket removal project. If you have a razor blade gasket scraper that isn't doing a good job try installing a new single-edge razor blade in it and see if your results change. Razor blades get dull fast when scraping metal surfaces with gaskets on them. Remember, the new razor blade will slice you deep if you slip while installing it in the scraper. Leave the shield on the end of the blade until it is installed in the scraper. Wrap the old blade in the shield that come off of the new blade. Wrap it heavily in electrical tape to keep it in place and carefully discard it in your trash.