Hi Adam.....
I prefer mine grilled, but I too have smoked them. I tend not to be a real big brining fan, but your results will improve 100% if you brine this cut.
It doesn't take much! Try this quick and easy brine...
3/4 cups Kosher salt OR 6 tablespoons table salt
6 tablespoons sugar
3 quarts water
Combine these in a 2 gallon ziploc bag. Make sure it all dissolves, it will do this pretty fast if you use Kosher salt.
Add the loin and marinate for 4 hours....no more.
Now, you can cook it at this point or rub with your favorite stuff and let it sit overnight.
As Jim says, and you probably already know this, take to a temp of 140-145? let rest for 10 minutes and slice away.
I started experimenting with this a few weeks back and I have made the best loins of my life. Matter of fact, I have one soaking tonight! I will rub down and cook it up tommorrow.
My next experiments will be with cherry juice and other citrus juices and salt. I buy these whole loins and then cut into 2 lb. chunks and cook them separately. Can't wait!!
Good Luck!