I use 3T of salt for 5 lbs of meat. The meat consists of 4-4.5lbs pork shoulder, and I usually add some pork fat to get to 5 lbs depending how lean it is. I would also suggest seasoning after you cut into chunks before you grind, then chill the chunks well for a few hours if you can before grinding.
Hope this helps,
P.S. Keep everything very cold!