hi nanty
Please, Please dont use any abrasive substance at all!
I am a coin collecter (numismatist) and as theprof says any cleaning will drastically reduce there value to almost being worthless.
If you do want to get the grime off them just soak them in distilled water and gently rub with a soft cloth.
If that does not improve them try soaking in a small amount of olive oil for a few hours and then rince it off.
Obviously they are your coins and you can do what you want with them, but as a collector i would rather purchace an unclean coin in worse condition than a cleaned or polished one in good condition.
Hope this helps you choose which way to go.