[Southern Home Boy]

Not familiar with IBCA, but I'll toss my $.02 in since you asked:

Brine, not injection. IMHO, birds take brine flavors very easily and direct injecting can either over do it, or discolor the meat in an uneven way. But be careful. You can over brine too. Make sure you rinse the bird well with cool, fresh water before you season it and to make sure you get all the extra brine out from under the loose skin.

Definitely rub under the skin. I make a compound butter with the same rub I put on the outside and smear that all under the skin; breast, thigh and leg.

Decide on sauce at the end of the cook. If you've got good color and moistness, I'd forego the sauce. If it's dry or you think the color is off, a good glaze can cover a variety of mistakes.