When I find a coin metal detecting Silver, wheat, or other copper. I use a Water Pic to remove the dirt. Even if it was a key date I feel the time in the ground will do more damage than removing the mud/dirt from the coin being in the ground. Many copper coins that are real old that I see are basically slabs. I see on many medal detecting sites they all say don't clean your key day/valuable coins. Am I doing any real damage more than being in the ground has already done? Is there a better way to remove dirt/mud? Ice
I wouldn't use a water pic. Why the hurry? I don't see any problem whatsoever with letting them soak in good old water. No one can argue with that. If that doesn't work, we call in the Coin Talk Secret Investigating Team. They're the "Coin Cleaning Police".
I do let them soak setting on toothpicks but that doesn't always work the water pic does pretty good on the coins soaking doesn't help. Ice
If they're for your own collection, I don't see a problem with it. I don't own a Water-Pik. Is the water really so forceful that it takes off stuff that a hot-water soak won't? If that's the case, you may be damaging the surface. If you sell the coins, I suggest that you describe them as being "dug", that's all.
Exactly why I do the soak then if nothing special the I water pic. The water pic isn't that forceful. Do you think I am damaging them more than being in the ground does? Clad I just run through a tumbler. Ice