Yeah, you can make your own seasoning, but that would involve you buying 6-8 different ingredients if you don't already have them. The premade seasonings are usually a bit on the salty side, but it is what it is.
As for the actual preparation, you'll need this-Cast iron, medium high heat and butter. Not oil, not margarine, butter. It's the combination of seasoning, high heat and butter that does it. Most flat-top grills in kitchens have a hot spot used for blackening, you'll make due with cast iron, which is actually better.
If you wanna do a fish fry, get yourself some wondraflour, great stuff.
As for other types of fish...simplicity is the key. Don't over complicate things, do things simple and right using the right flavor profiles and remember, when you are not blackening/frying, hot fish is overcooked fish. The other day at work I had free range to cook a so so fish, tilapia, my way, so I laid them out on sheet pans, seasoned with salt, pepper and dill, then added white wine and lemon juice to the pan, about a quarter inch worth, and topped them with a little melted butter, more or less poaching them in wine. This went into a 250 degree over for about 10 minutes, until they became opaque. Came out great.