What you need:
(Recommended) A level 70 character.
(Recommended) Auctioneer to know how much to price Fiery.
Where you are going:
BRD of course =D
To be specific.
Guide:
It's pretty simple if you just follow the picture, but you have to go through the top level of arena. Here it goes-- Head to Black Rock Mountain (BRM), zone into BRD. Then just follow the map... He is a rare spawn so he might not be there every time you do this, but when he is he usually drops the Formula (Thottbot World of Warcraft: Formula: Enchant Weapon - Fiery Weapon). If you need more help I'll make a video once I get a good screen recorder.
Aftermath:
Do not flood the auction house with these, I would suggest saying on your trade channel that you are selling it but don't mention how many you have or they will think something is up. Sell them for the auctioneer price and if it says "Never seen at Auctions" then just make a reasonable price.
Thanks,
Pimpin_N0ob
P.S- Sorry for bad details on how to get to him haven't been in here for a bit, I will run it later.