the reason you use an aged coin isn't so much for the look its because an aged coin in softened, so the coins make less noise when performing. I have tried many different methods to soften coins. I use a whetstone lightly rubbing the coin in a figure of 8. Depending on what the coin is, makes a difference on how far you can rub the coin down. If they are silver then you can get them pretty soft, if they are plated then you have to be careful otherwise you will rub down to the base metal. Generally I will rub them down a little bit then use them a lot and carry them in my pocket all the time, and just let them naturally age. It will take time naturally to age them but with a lot of use and carry not as long as you may think, especially plated coins.