Duck Fat is not a good fat though it is a highly respected way of cooking food. It is high in cholesterol and not recommended by doctors or nutritionists to use in cooking. Chefs love it of course and it can be useful in frying or sauteing potatoes, legumes or other vegetables.
If you prefer flavour and want to cut down on cholesterol then use 1 tsp of duck fat to 1 tablespoon of olive or canola oil. It will give your veggies a nice flavour, but will reduce the amount of saturated fat and cholesterol in your diet.
It won't help your waistline, but this is one of the most common ways to cook potatoes using duck fat.
About a pound or two of potatoes can be used.
Rosemary or Thyme (tablespoon each if fresh, a teaspoon each if dried)
Heat the oven to 425°F/220°C. Toss wedges or slices of potatoes with 1 tsp of duck fat in a bowl and 2 tablespoons of canola oil in a bowl. Sprinkle with sea salt, pepper, and dried or fresh thyme or rosemary. Bake, stirring occasionally, until the potatoes are very browned and crisp, 30 to 40 minutes.
The bottom line is if you are watching your cholesterol, you should avoid most animal fats in general. Canola and Olive oils are good to use as they have a good balance of mono, polyunsaturated fat content. Olive oil even has the benefit of flavanoids though has a lower smoking rate, and isn't good for frying as Canola is.