Being that I work in a millwork factory, I have ready access to hickory scraps
I use a gas grill for ease of use and speed, but I put a tin can full of hickory chips down inside the grill just above the burners. The chips smoke, but don't flame, and add a great flavor to anything that I'm cooking on the grill
I make the hickory chips by feeding the scraps (after ripping them down to 1" x 1" sticks) thru my branch chipper (thank you Troybilt

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