The first thing that you learn as a coin collector, is that you should never under any circumstance clean a coin. You cannot increase the value of the coin by cleaning it, you can only lessen the value. The metal surface of a coin will always carry come indicator of a cleaning, some collectors this "damage", no matter how expertly performed. You may not be able to detect a cleaning, but an expert with a microscope can.

If you are never going to sell the tokens, and if they look really horrible now and if they have little value, you might consider cleaning them. I would first determine what substance is on the tokens and the proper way to clean them. You can go to a local coin show and get some advise from a dealer. It is not always possible to clean a coin without doing really noticeable damage to it. That's why you need expert advise. You might otherwise wind up with something that looks worse than it does now.