I am working on removing the "grime" from the Luke X-wing helmet.
I am using a mix of acetone in small applications. The results are great so far. The one on the left is the one I am working on, the helmet on the right is stock.
Be careful, if applied to heavy it will remove the helmet markings. I plan on repainting mine, so im not too concerned if I lose some paint.
I began repainted Luke's helmet today. It's a start. Going to work on it some more over the weekend. I may dull it down a bit, not sure. His helmet was pretty battered in ANH.