Ashamed to admit it but aint never tried cooking a tame duck breastes. Plugging the phrase "duck breast smoker grill" into google got a bunch of hits from folks claiming to know how to do it right. Outdoors seems to be the preferred method. Kindly let us know how it turns out and it could rate a person a nomination as the official duck breastes exspurt around here.
I'd treat 'em just like chicken breast, except a little ginger root, curry and soy sauce with olive oil under the skin, instead of chicken rub and butter.