I've never tried water oak, but as aawa pointed out, if it was cut down recently it won't be seasoned yet.
A far as the brisket, 12 hours is plenty of time if you cook hotter. You didn't mention what you cook in so it's hard to make specific recommendations.
For the open turn in, how many people do you have to feed? Is it just a few judges or everyone? If it's just a few judges how about Tri-Tip?
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