Honestly, I don't collect numismatic coins, so what I say here isn't from first hand experience. I do collect bullion coins though.
In the case of numismatics, my understanding is that any sort of washing or cleaning in a non professional manner is highly frowned upon, as, if it's not done correctly, it would potentially ruin the value of the coin in question.
If these are bullion coins, on the other hand, I wouldn't bother washing or cleaning them in any way. Some toning on certain products (eg. Perth Mint bars) is quite acceptable, and purchasers of these goods are buying them for the 10oz of silver, and generally don't care if there's any toning involved.
On the above basis, I've never cleaned a bar or a coin, so with many apologies, I'd have to say I can't answer your question directly, other than to question what it is you're looking to achieve in your cleaning operation to begin with?