I use prunes and apples. You peel and core and slice cooking apples, two or three for a duck, six to eight for a goose and about twenty prunes. If they are the stoned variety they should be soft enough just to pop in the bird, but if they are very dry, soak them overnight before stuffing the bird.
I make my own forcemeat stuffing using either pork mince or pork and veal minced and mixed, salt, pepper, one or two eggs and a cupful or two of fine breadcrumbs.
You can use a mixture of beef mince and finely minced ham if you prefer. Minced chicken tends to become rather dry, so add a good tablespoon of lard or margarine to it (or cooking oil, if preferred)
Any forcemeat that is not need to stuff the bird, can be baked in a pie dish in the oven for the last half-hour the bird is roasting.