I have a 50 8N and have removed the lift cover and the pump. The gaskets are stuck on real well and I don't want to be too aggressive scraping them off and damaging the surfaces. What is the best method for cleaning them off? I found a 3M Scotchbrite product called Roloc bristle disc and wonder if anyone has tried them. They come in various grits from 50 to 120 and are color coded. I also see chemical products and wonder how well they work.