Read the label and see if that breast is already brined. It's getting hard to find turkey at a supermarket that doesn't says something like "Contains up to 15% broth" or some such. Brining it could make it too salty.
My go-to procedure on turkey breasts lately has been to soften a stick of unsalted butter, and mix it up with your favorite rub. Loosen the skin on the breast so you can get your hand WAY down there, and slather that butter/rub under the skin. Put more rub on the outside of the skin. I use a small skewer to hold the skin in place while I smoke it. I put a drip pan on the next grate down to catch all of the goodness dripping out (mostly butter) and the wife makes gravy out of it. Smoky, buttery gravy- YUM! This makes the juiciest turkey I've ever had.
I'm very intelligent, but I mask it by doing stupid stuff.