The best way, especially silver is to just rinse them off. With Large cents I use dish detergent , soak for as long as you want, let it dry and lightly use a toothpick to get some of the dirt and dried patina off. I have 5 2-cent pieces and they are very green, but that's what holds the detail. Indian heads are hit or miss. I find that the older ones are tough. Can't do much to them. The ones in the 1870's up, I use the method that I use with the large cents. One side is always better than the other,I hate it when the better side is not the date side. The coin as my avatar has been altered so it looks more brown because its too dark otherwise, but the patina makes all the detail come right out. It's a dark green.