MUST do it outside. Way to much smoke when you do it. HOT ass cast iron skillet, run the fish in some melted butter then a very heavy coat of your favorite blacken seasoning. I like Paul Purdomes. Next into the hot dry skillet. It will smoke like a SOB, only takes a little time on each side. Only flip once, the more you flip them the more of a chance of having your seasoning come off.
That's the seasoning and method that I have used, though in recent years I have switched to Olive oil for supposed health reasons. I can't tell any difference in how it tastes. At home, I put the skillet on the fish cooker and get it as hot as possible. When traveling, I have used a Coleman stove. It takes a little longer with it, but it works.
Anyone got a suggestion on a cast iron product bigger than the standard skillet? I've thought that I could cook a lot more fish at one time if I'd buy a bigger cast iron pan or something. Anyone use something bigger than a skillet?