GLASS BEADING INSIDE OF VALVE COVERS AND OIL PANS

If there is rust on the inside I would just use Evapo-Rust. I have gallons of that stuff sitting in the garage, and I immerse rusty parts in it, and when I remove them a couple of days later the rust is gone. Have had it for years, and since it is reusable it is mostly a one time investment, but an expensive one as one gallon is like $30. Since it last basically forever, in the long run it is not too bad of an investment. On the outside of the valve cover you can use a wire wheel on a drill, sandpaper, etc...