I have done chicken and bone-in turkey breast with a East Carolina Mustard Sauce. I did not brine or inject, but did let the Birds swim in the sauce for 12 hours, and then added rub. turkey breast was tender and juicy.
That is my current dilemma right now - Mustard Sauce, on Turkey that is brining, or Apple Butter.
Apple Butter is sweet from Fructose. Fructose begins to caramelize and then burn at 230°F or higher. So unless you smoke that bird at 225°, it will burn. Go with the Mustard Sauce, as long as it is not Salty. Brined birds need no additional salt in toppings or Rubs...JJ