I'm bad...I clean my silver coins too...if I know they aren't worth more than the silver content. I use a bowl...line it with aluminum foil...hot water/baking soda and salt...let the coins soak for about 5 min...then I use a very fine microfiber cloth to buff the coin surface to remove the tarnish thats been loosened up.
Btw, only clean the 1965-1969 halves, because the 1970 has a premium that will get destroyed if cleaned
The 70-D isn't the only one that has a premium. My dad found me a 1967 DDR-001 Kennedy half dollar looking through a bunch of junk silver which graded MS65 at PCGS (several of this variety for the grade has sold for between $550 - $700)
I'm trying to eliminate most of my coins and just concentrate on fewer high quality pieces. I'm doing this with my paper currency as well. It will make it easier on my heirs to divide up or sell, if they choose to do so.
No actually pure sulfuric acid is the best , just don't pull them out with your fingers . lol Or you could use a sandblaster , it gets in those tight spaces without any problems .