I'm way too lazy to double grind. I always mix the spices with liquid...beer water 7-up or Sprite also works well. Then dump it on the cut up meat and mix well...then I grind it and mix it well again. As Joe Ames say you need to mix it till you cant mix it anymore..then keep mixing. Want to mix it till it gets "bouncy" i.e. sorta fluffy feeling..then stuff. Only exception is if you want to use whole peppercorns for summer sausage or salami or whutever. Need to add them after grinding or they will get hung up on the back side of the grinding plate. Now my old pal Big Jim down in Floriddiy swears by grinding and stuffing all in one fell swoop. You cut the meat up..spice it..grind and stuff. He used to make a lot for a bbq restaurant he ran and he claim its the only way to fly. He was using just slightly less than a commercial type electric grinder. If you want to do it like that..think you need to have the meat cut fairly small and uniform...or stands to reason you would. Did not sound like he was real picky about it. He just needed a bunch of good sausage as painless as possible.
bigwheel