Cleaning gasket surfaces using 3m disc,razor blade,x-acto knifes and Arkansas stone.3m cleaning disc’s come in different sizes,shapes and grits. i have found it easiest to use on a 90 degree high speed grinder using light pressure and being careful not to overdo it. stop once gasket material is gone. (lower photo) Using a Arkansas stone lubricated with mineral spirits to lightly touch up,clean or de-burr rough edges of a surface. It is best to use the finest grit stone possible to accomplish the job while using light even strokes. Most aluminum surfaces are fairly soft so you have to be careful and use good quality tools and equipment.