Though I don't do beer can anything it's not for that reaason that I wouldn't suggest beer can duck--at the very least not without substantial prep. Commercial duck is very fatty. Whatever way you cook it you'll need to plan on catching the rendered fat.
Normally, I bone out the breast and remove the skin from everything but the leg quarters. The skin--with its attached fat--I save in the freezer till I have several, then I render the precious fat, make rilletes of the skin. The breasts I grill, rubbed, to medium-rare.
Anyway, for roasting/smoking: Bring a pot of water large enough to contain the duck to a boil. Meanwhile: Trim all extraneous skin/fat from the duck, i.e., any that's just hanging there--don't remove the skin from the flesh. With a sharp-tined fork or a thin-bladed pointed knife, pierce the skin all over the duck--skin only, don't go into the flesh.
When the water is boiling, dip the duck into the pot and leave it for one minute. Remove the duck, wait for the water to boil again, dip again for 1 minute; repeat once more. Pat the duck dry then place in the fridge, uncovered, to dry out the skin, at least overnight.
Pierce the skin again before cooking. Bring the duck to room temp before cooking. Roast/smoke at 325 for 2.5-3 hours . If the duck is not browning nicely after 2.5 hours, bump the heat up to 375-400 get better color and the skin crisper. Rest the duck 20 minutes after removing it. To get the skin crisper for serving, if desired, heat a quantity of oil till very hot in a pot then ladel the hot oil over the duck skin right before serving.