Do you mean tear stains or other marks in general?
If you mean in general, we use the Wahl diamond white (forget exactly) for general shampooing which brings him up a treat. I've previously also used the Groomer's Blue Pearl coat enhancer. You can get both from Christie's online or Amazon I think.
When it comes to tear stains and some staining on some of his toes the only thing we found that really helped was regular (almost daily) washing with a 5:1 ratio of hibiscrub left for a couple of minutes then fully rinsed out. As it's cosmetic only (and I've been lazy) the stains are back.
I did try the diamond eyes product once but I have to say, we got better results with hibiscrub so I haven't bought it since.