So, we made it. And the results were better this time around.
For starters, I found a better brining bag. An actual zipper bag made for that. It was much sturdier and larger, so it held up to more abuse.
I left the ice packs on the breasts for about 30 minutes this time instead of 15 to 30. I also iced them prior to brushing on the olive oil, black pepper and garlic powder.
And last, I used a full load of coal. So no trouble maintaining the temperature for the duration of the cook.
The first pic is after about 2 hours. I went ahead and tented the bird with foil at that point. The second is after about 3 hours and 10 minutes, right before letting it rest. After the 15 minute rest, I carved it immediately.