Its all in what you want........ you can either low and slow or fast and hot. Your IT is 165 to shot for at middle of the thickest portion of the breast. You can brine, inject, and rub all bringing flavor modifiers to the breast.
Personally I would brine the breast, no it doesn't add moisture, its to add flavor. Basic brine is 1C of salt, sugar, brown sugar to 1 gal of water. Me I use more sugar and less salt. It all depends upon how big the breast is. If it will fit in a 1 gal ziplock, I would mix up 2 qts water, 1/3C salt, 1/2C white sugar, 1/2C light brown sugar, and your choice of flavor modifiers, parsley sage rosemary thyme garlic onion etc ..... Don't go overboard, I suggest you pick only one or two, if you use 'em all the flavor becomes all muddied up. I would probably no more than a Tbsp of your flavors.
Heat a Qt. of water, add your spices and herbs, and make sure those dissolvable are dissolved. Add ice to cool it down and top off with cold water to equal 2 qts. total. Clean and wash the breast, put in the ziplock bag, pour as much brine as possible in the bag and seal it. Let it sit 24 hours.
Pull rinse and pat dry, return uncovered to the fridge for 4 to 24 hours to dry.
Smoke at 300 to get a crisper shin although it may not need that long a cook to get to 165 IT. Myself I would do a low and slow, maybe 200 to 210 and get there slowly. Either way works, low and slow to me means guaranteed tender out of this word. But everyone has their opinions upon this. Although it is a much longer smoke.
I understand gorilla fingers.
Ok, with your propane you'll more than likely go fast and hot, I use 300 to 325 and its still a 165 IT
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