Rhys,
First any polish will do just that to the fittings, polish them up nice & shinny and leave a less than desired result.
May i suggest using Nu Finish car wax or Ren wax, these will remove the green stuff, not affect the metal in any way, leave the natural patina intact and not polish up the fittings like semichrome or flitz. At least it's worth a try before you take away the character of the dagger forever.
Eric Wien
