How do you get the Mirror Shield in Legend of Zelda Majora's Mask?

To get the mirror shield you have to fuse kinstones with the mysterious walls (all of them) them you have to fuse kinstones with one of the gorons in that cave and the big goron will appear he may not offer this at first but after a while he will he will want to nibble on your shield hand over your shield and come back a little while later. He will spit it out and you will have the mirror shield.

The above is right, but it isn't after a certain amount of time. If you talk to the big goron he will say something like "come see me after you do something important, O.K." by which he means, after you beat the game. So, when you beat the game and it asks you if you want to save, say yes. then, in the title screen, (if you saved) there will be a little gold triangle, and that's your ticket to the mirror shield and the last 6 figurines. Actually, according to the official Nintendo Player's Guide. you need to beat the game twice.