I'm almost 100% on the rim check on halves. With that being said, I have around 10 silvers that would have gotten dumped if I wasn't sound checking, too. The sound check does not really add much time to the hunt. I get through a box of halves in 10-15 minutes by rim and sound checking. I could probably trim that down to 7 minutes if I didn't sound check, but it's not worth it for me. I've had all kinds of silvers that look nothing like silver. From black, to brand new clad-looking, to dirty brown, to green. The rim check is reliable, but it is not 100%. I don't think the sound check is 100% on its own either because I've been getting a run of the really rounded edge worn out halves that sound almost like silver depending on how they are dropped.
When I started I would date check every coin. Not only did that take a ton of time per box, it also meant that I wasn't checking mint marks, which made that hunt even less reliable than a rim or sound check. For you guys that check every date and mint mark I give you credit for having incredible patience. If I had tried that when I was getting 20+ boxes per week I would have had to quit my job.