For the razor, keep it at a shallow angle (I tend to go around 20 or 30 degrees above the stovetop), and keep a small amount of water on the surface. I usually have a damp rag that I wipe the razor and stovetop with occasionally during the scraping process, to remove the small pieces that come off.
Also, if you are nervous about damaging the stovetop itself, maybe try something only lightly abrasive and warm water, and let the water work it’s magic. (I see you have already tried this, so maybe that isn’t helpful :/ ) From a chemistry perspective, salt water shouldn’t exactly leave behind an insoluble residue, but IDK what else was cooking in the water.
I’ve used a razor for really stuck on bits on our glass top stove, but this cleaner also seems to do quite well: https://weiman.com/glass-cooktop-cleaner-polish
For the razor, keep it at a shallow angle (I tend to go around 20 or 30 degrees above the stovetop), and keep a small amount of water on the surface. I usually have a damp rag that I wipe the razor and stovetop with occasionally during the scraping process, to remove the small pieces that come off.
Also, if you are nervous about damaging the stovetop itself, maybe try something only lightly abrasive and warm water, and let the water work it’s magic. (I see you have already tried this, so maybe that isn’t helpful :/ ) From a chemistry perspective, salt water shouldn’t exactly leave behind an insoluble residue, but IDK what else was cooking in the water.