John, some disagree but I'll say that, based just on my own cooking experiences, you CAN go ahead and brine that breast in a well-seasoned-up brine for 12 hours or so with no ill effects. (1/2 gallon liquid, 1/2 cup Diamond K salt OR 3/8 cup Morton K salt, 1/2 cup sugar (brown, white, or mixed), plus copius amounts of Chipotle Tabasco, cayenne, or whatever else trips your trigger). I wouldn't go a full 24 to 48 hours on the brine, though. You won't get as MUCH flavor from the brine as you would if your bird was natural, but you will get partial flavoring effect. I brined a number of Honeysuckle White bone-in breasts about that same size for people during the week before Thanksgiving, and they turned out great, pumped or not. It was an apple juice-honey brine, and the taste WAS lightly transferred into the meat, with no excess salty flavor and NO mushy meat. The natural turkeys that I did in the same brine solution pulled more of the flavor of the seasonings, of course, but I had no problem with the brined pumped birds. Just my opinion, though - many don't like to brine a pumped bird at all, so you'll have to see what you like and what works for you.
I don't like to inject (just my 'druthers), but I agree with Doug on gently prying up the skin and smoothing a little rub up underneath. I like to add quartered onions and apples, chunks of celery about 3 inches long, a few chunks of carrot, and some big springs of sage to the cavity. I have a big sagebush just outside my backdoor for just such occasions...
I also start out the breasts meaty-side down for an hour or so, and then flip them over to breast side up for the rest of the cook. When you remove it from the smoker for its little rest before eating, wrap it tightly in HD foil and rest it meaty side down until you're ready to eat, leaving the onions/apples/etc inside until you unwrap it for serving. The juices will tend to work back down through the breast meat that way.
That being said, you CAN just throw that bird-breast on the smoker naked as it comes out of the package for a couple of hours, breast side up, and not do a THING to it, and it'll come out just great. Just don't let your meat temp get much over 160. I like to pull it when the breast meat is between 155 and 160, personally.
Keri C
Still Smokin on Tulsa Time (and sharing her 2-cents worth with the world at large)