[phatch]

Brining is a popular treatment for pork tenderloin. I usually don't however. For me, this is more of an off the cuff quick main course than something I plan far enough ahead to brine. The main thing is to cook it so it's still pink in the center. Stop cooking when the meat is about 140 degrees in the center and let it rest before carving.

It's an odd choice of smoking in many ways unless he wants canadian bacon out of it. It's too lean and better suited for quick high temp techniques. Not to say it can't be smoked to a proper finish.

If he wants a smoky flavor, I'd cut it into thick medallions/steaks, wrap with bacon and do them on the stove top. It's probably my favorite way to cook this cut of pork. America's Test Kitchen does a good version of this but they've hidden it away in their premium content now. They have lots of other tenderloin recipes you might look at as well though. You do have to register; it's free and only needs and email address as I recall. The premium content you do have to pay for but lots to see for free still including some grilled versions.

If he want's it literally smoked that's trickier and I've not done it. This is the approach I'd take however. I wouldn't brine. Could be too hammy/canadian bacon-like for how I prefer this. Just FYI, I'm on reduced sodium diet so that could easily be influencing what my preferences are.

I'd do this with a light rub. Tenderloin isn't a strongly flavored cut and so I want it's character to come through.

1 tablespoon garlic powder
2 tablespoons onion powder
1 tablespoon paprika
2 teaspoons kosher salt--to taste--I'd personally use less
1 teaspoon black pepper--to taste--I like black pepper. It makes up for lower salt
1/2 teapsoon dried thyme
pinch of rubbed sage

mix the rub ingredients together. Rub the meat lightly all over with the rub.

I'd set up my smoker for a heavy smoke and only smoke it about 15-30 minutes. it won't have a lot of smoke intensity but that wouldn't be right for this dish anyway.

Then finish in a pan on the stove, browning it on all sides. Take it out of the pan at a temp of 140 in the center and let it rest 10-15 minutes before carving.

Certainly a pan sauce would be good with a touch of barbecue sauce to match the smoke.