Paul, not related to your question, but a friend and I made sausage together for the first time last weekend, and I learned a couple of things that you might find helpful.
To distribute dry spices, he suggested using a shaker. I have a large cheese shaker, like you'd see in a pizza shop (large holes), that really worked great to shake the spices evenly over the meat. Much easier than trying to evenly spread by hand or shaking from a spoon.
The second thing he did that I thought was a great idea was, after the first grind, he spread the meat in an even layer on a sheet pan. We applied about half the spices with the shaker. Folded the meat to make three layers. (Could also roll the meat, I suppose.) And then mixed the meat a little bit. Spread the meat back out on the sheet pan. Applied the rest of the spices, folded, and mixed the meat a second time. Then into the grinder for the second grind. Nice, even distribution of the spices. Minimal working of the cold meat (easier on the hands).
A third thing we did was to apply certain spices separately. We were making some of Kirby's summer sausage, which is seasoned with a lot of mustard seed, various dry spices, and what I'll call wet spices, that included liquid smoke, minced garlic, and water for a carrier. The last time I did the summer sausage, I had a hard time with the mustard seed, which wouldn't blend with the rest of the dry spices due to the difference in particle size. This made it hard to evenly distribute the mustard seed. So, this time I mixed and spread the ground dry spices. Spread the mustard seed. And then spread the wet spices. Three separate, consecutive spice application steps. Folded and mixed the the meat after first three spice applications, then repeated the three steps for the second spice application and lightly mixed the meat a second time.
Between spreading the ground meat into a sheet for spice application and applying the spices by particle size/density and dry vs. wet, we seem to have gotten a really good distribution of the spices with minimal mixing effort.
We were working with a five pound batch, so the half sheet pans that I had on hand worked OK for spreading out the meat. But, more space would have been nicer and would have allowed a sheet of meat thinner than about 3/4 of an inch, for even better spice distribution. The local restaurant supply house is having their annual sale this weekend, so I've got a full sheet pan on my shopping list to give more room to work. And another shaker, so I have one to use for ground spices and a second shaker for applying the larger particle size spices.
