During the cooking/smoking, neither.
We prefer the firm, almost crisp meatloaf "bark" rather than any type of glaze. You can always add gravy (our personal choice, as what is meatloaf without mashed taters & gravy?!?!
) or bbq sauce after plating.
After my 1st attempt at smoked meatloaf last weekend (fortunately, a BIG hit!), I doubt we'll go back to regular oven-baked meatloaf until the winter weather forces us inside.