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You learn the Chocobuckle Enemy Skill from a Chocobo. ^^
Here it is..
Put every single Enemy Skill materia you have one only one character.
Go to the Grasslands Area, if you're not already there. Run around, but not on the Chocobo tracks area (mainly the light green grass surrounding the Chocobo Farm).
You need to get the L4 Suicide Enemy Skill first. If you have it already, you can skip this part.
The L4 Suicide skill is found on cute little squirrel creatures called Mu. You can't manipulate them and they are also rarer than most creatures out here. When you find one, avoid killing it off and wait for it to use L4 Suicide on you. Since it affects all your characters, you don't have to worry about putting the Enemy Skills on all of them (assuming you have more than 1 ^^).
Once you've got the L4 Suicide, enter the farm and talk to the guy inside the stables. You'll need to buy three Mimett Greens, the most expensive one there is. If you like, you can buy more in case you screw up. =P
Go outside again.. Make sure somebody's got the Chocobo Lure and start running around on the Chocobo Tracks. Eventually you'll enter a fight with a Chocobo. They'll usually be Level 13 Chocobos. If that's the case, end the fight somehow and start running around again. You need to get into a fight with a Level 16 Chocobo.
There's an easy way to tell if you're in a fight with one. The same enemy (usually a Levrikon) will be on either side of the Chocobo. If not, it's level 13.
When you see a Level 16 Chocobo, quickly have all your characters feed the Chocobo the Mimett Greens. You need to feed it three of them. No more, no less.
Now get whoever has the Enemy Skill materia to cast L4 Suicide. When it hits the Chocobo, it'll use the Chocobuckle enemy skill on the caster. Since you've (hopefully) already put all the Enemy Skills on that person, he or she will gain the Chocobuckle skill on all of them! ^_^
Ta~
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