I tried my first last night. I'm using an oven. So all I did was put some olive oil in a baggie, add a bunch of pork rub, and then marinated my tenderloin overnight (and all the next day).
I then put that mofo in a skillet and browned the outside, preheated my oven to 325, placed my pork slab in a glass cooking thing and covered it with Al foil. Everything online said it would cook in 10-15, but after 10 I took it out and added KC style BBQ sauce to one half (I was experimenting), and it was not close to done. I put it back in, turned it up to 350, and left it another ten minutes. Checked it again, wasn't quite done but close - I swirled my BBQ sauce just so I felt like I had done something, and put it back in for 5 minutes.
Now here are my questions for your pro cookers out there.
It was a little pink inside, and pretty juicy - so I was happy with that. The half with BBQ sauce was way better, the half with just pork rub was a little bland. My issue is that all the flavor was on the outside crust, which is a very very small percentage of each slice. Is there a good way to get more of that inside? If I slice it before cooking it will be too thin and dry out I think. Do I just marinate it longer? Should I marinate it with BBQ sauce?
Overall it was very good, but I'm looking for something more in the awesome realm.
EDIT: Oh, and what the fuck is brining it? Do I soak it in salkwater for a night, then marinate it for a night?
If you get the ones that are all one piece (i.e., handle is also cast iron), you'll probably give yourself a pretty awesome burn on your hand at some point before you get used to using a mitt to fry, or just not touching the pan.