limon juice will probably over clean it and leave some areas
pink or unattractive . I suggest soaking in distilled water changing the water daily for a few weeks and see if it brushes off with sop and water via a cut down by half toothbrush..... while it's
still wet you could gently try and
pick at the green witha toothpick or the non business end of a matchstick. Or you could do the same long soak with olive oil and you won't need to change it much. Others would suggest using mechanical efforts and those are described in detail on several threads.
