You can add ingredients to the ground meat and stuff right away, I recommend that, then let sit in the refer overnight or longer for a quality sausage...
Speed in processing affects quality...
The reason we advocate the curing procedure is that this book is about making quality products and quality takes time. Meat for quality smoked sausage should be cured. Curing imparts a certain peculiar flavor which is in demand by the consumer and if we cure hams, bacon, chops, butts, and fish because they taste better, so why not cure meat for sausages? The fact that we grind meat makes it only easier on our teeth to chew it - it does not improve the color, texture or the flavor of the sausage. Someone might say: but I’ve mixed nitrite and spices with ground meat before stuffing so that’s OK. Well, it’s not ok, the problem is that not enough time was allocated and the sausage is only partially cured. The dry method of curing is used to cure meat for sausages. The curing time depends on:(what PolishDeli said)
Marianski, Stanley. Home Production of Quality Meats and Sausages (Kindle Locations 3464-3471). Bookmagic LLC. Kindle Edition.