Hey Adrian: I keep roughly 10-20 coins, in progressive stages of cleaning, in each of four tupperware containers soaking in DW almost continuously. Some may soak for more than a year. I change the DW roughly every few days or weekly in the early stages; less frequent in later stages. Few coins will clean up with only DW soaks and brushing or toothpick prodding. Most will require mechanical cleaning. I clean under an inexpensive 10X microscope and prefer an exacto knife using the no. 11 blade (inexpensive) and diamond encrusted dental drills in a pin vise (pretty expensive, but cut off needles and pins
work well
good too). Patience is the key-- remove the easy dirt, soak some more, remove a little more dirt, soak some more, and so on.