[richrussell]

If the cloth looks like it's still sturdy enough (ie not brittle and likely to tear), then I just soak it in warm water with a bit of non-bio washing liquid for a couple of hours, then gently brush it with a nail brush and rinse. That usually lifts the dust and grease that accumulates without making the cloth look out of place with the patina of the rest of the set. Then refit it (glue if necessary).