I have never taken an animal to a processor. I was taught from a young age to handle wild game from the field to the table. I cut, grind, wrap and freeze it myself. When I get venison ready to grind I remove all fat and silver skin. For burger I grind just the meat. If I'm making sausage I will add a little pork fat to the meat as I grind it. I normally make sausage in 15 lb batches and I use 13 lbs of venison and 2 pounds of pork fat per batch. I want to taste the venison and not the pork.
I can get pork fat for very little cost from the store and I put it in the freezer until it is about half frozen. At that stage I can cut it in small pieces and mix the cut up fat with the trimmed meat and I grind it all together. When the fat is cold it doesn't congeal on the grinder plates and is easier to disperse in the meat. Depending on the seasoning I'm using I may or may not grind the meat with the seasoning already on the meat. Like I said, it depends. Grinding the meat after it has been mixed with the seasoning ensures the seasoning is throughout the sausage.