Reddit mentions of Mag-Nif Digital Coin Sorter

Great questions OP. I will shamelessly plug /r/CRH, but also update my sidebar to address some of your questions.
There are cheap coin sorters like this one if you do not have a local bank that provides free coin sorting services. As TheDude66 says, looks down the edges of all coin denominations 10cents and higher for the dead giveaway white edge.
I don't think there are any accurate statistics on which denomination is most likely to have the "right" dates, but if you start following some of the posts around here, you will find that a lot of it depends on where you live, how many other coin roll hunters are in your area competing for silver, and other factors like if the banks are getting rolls of coins from a company like brinks that might pre-sort any silver coins. I personally like searching dimes because they are light for their denomination, are quick to search and quick to return to my bank. Others like half dollars because of the bigger payout for when you do find a silver coin.
I am very certain that 40% silver coins do not have the bronze edge, and would be easy to spot versus the newer clad coins. I hope this helps, and I hope you get some silver from that pocket change. Otherwise, go to the bank and grab a few hundred bucks in coinage!