Goose do require a modest amount of fuss in prep. After that they are no more challenging than turkey. Thinks I.
First item: Have two roasting pans and a rack that allows for easy transfer of the goose from one to the other.
Fetch your goose, between 8 and 12 pounds, early enough to be completely thawed by the time you mean to prepare it for cooking. Wear expendables: grubbies or a working apron. Roll your sleeves up. You will get intimate with this goose which always means a bit of mess.
Preheat oven to 350of. Unveil the goose from out of its packaging and rinse it. If the innards are in the cavity, remove them and reserve. Inside one end will be two great wads of fat. These pull away easily. Do so and reserve them to render later for deep frying oil. Slide your fingers or a rubber spatula (I end up using both) between the skin and the meat. Try not to break the skin. Do this all over the trunk of the goose. Prick the goose with a fork all over through the skin BUT NOT INTO the meat. Spoon as much garlic as you like between the skin and the meat. Salt and pepper ad libidum inside and out. Collect a bouquet garni of sage, thyme, rosemary and what-have-you-else. Add the leafy end of a celery rib or two and a halved onion with its dried outer layers and ends still attached. Shove all of this into the cavity and place the bird breast side down on the rack in the first roaster. Cover with a tent of aluminum foil, shiny side in to reflect the heat. Convey the goose into the oven.
That is most of the fuss.
Let the bird render for one to one and a half hours, until you have at least an inch of fat in the roasting pan. Set the innards to simmer in a pot of water, with a bay leaf crumbled in, covered, for about an hour. Meanwhile finely dice a small onion, a rib or two of celery, and a carrot. Place this in the second roasting pan with some garlic, sage, thyme, etc. When the hour expires remove the first roaster from the oven carefully to not spill any of the quart or so of hot fat you now have. Place it in an out of the way spot where you can leave it 'til the next day. Transfer the goose to the other roaster. Turn it breast side up. With its foil tent tucked in put the bird back in the oven for another hour to two hours depending on the size of the goose. You can tell it is done by how freely you can move a wing or a leg in its socket. Remove the foil tent and rub the bird with a stick of butter (or brush melted butter over the skin). Return to the oven for fifteen minutes, or so, until the skin browns and crisps to your preference. Remove from oven and transfer the bird to a carving platter and let it rest for twenty minutes or so, before carving.
Whereas the first roaster was filled with mostly fat, the second roaster should contain a nicely browned collection of vege, juice and fat. Pour this into a blender or food mill and whiz it into a puree. Add a tablespoon or so (depending on thickness desired) of flour while it whirls. Deglaze the pan with a half cup or so of tawny port. Add to the liquefied vege/drippings mixture in a frying pan or sauce pan, and heat. Stir frequently as it nears the boil. As it thickens add buttermilk (about two cups) and, or, the water the innards simmered in (about one cup), to the gravy. You can add the heart and liver to the blender, or not. Or feed them to the cats or dogs.