My go to maranade for duck is equal parts Kraft Rosted red pepper itilan dressing and Alegro either Game Tame, Gold Buckle Brisket Sauce or Hot and Spicy what ever you in the mood for, then add in a few chopped up cloves of fresh garlic.
I like to cut the duck brest pice into 2 or 3 pices depending on the size. Then take a meat mallet and pound it 2 or 3 times on each side. Marnade them for a few hours or over night if you have time. Then wrap with a 1/3 or 1/2 pice of bacon, cook on med high to high heat. Its best if you can get the bacon done and the meat is still Med to Med rare.