Done a few briskets in Open Range pits. Go with lump. For wood, 2-3 fist size chunks. I would put a foil pan in the bottom of the smoker box with water. Easy to refill. If you choose to do this refill with HOT water. Two reasons, it wont steam back on ya and it will not cool down your smoker box temp.
Start probing with a toothpick after the stall (170-175) when that pick comes out clean and goes in and out early, remove it from the OP. Let it rest for at least 1 hour. I double wrap in foil and wrap in a bath towel. I will go two hours.
Oh, run the Open Range at 250 for the entire cook.