First step is to store it out of the sheath for this very reason.

The metal surfaces can be cleaned up with Flitz or similar. When done cleaning it up, coat it with a light layer of Flitz and dry-wipe it clean with nose paper tissues. That process will leave a micro-layer that'll protect the metal.

I think someone had posted a means to get the green gunk out of the leather, but I can't remember it. I'm still grinding through my morning coffee.