The reason you use soft bristle tooth brushes to clean critical contacts on aircraft electronics is that not only will this remove oils, dirt, and corrosion, but it will also remove the thin coat of oxidation that adds resistance to the connection. That way the electrical connection is improved. But it is this very coat of oxidation that is part of a coin's surface, even containing part of the original metal. And collectors want that left on. Even if you can do it without hairline scratches (which I do not believe you have accomplished on this coin), you have defaced the natural finish, giving it a "polished" appearance. There are very few exceptions to the "NEVER CLEAN" rule. Someone mentioned ancients, which usually are found caked with dirt and/or corrosion, and there are certain coins which are oily or dirty that can be improved with a very careful dip in the right solvent, usually acetone. And welcome to CT! People here really aren't trying to be obtuse or unfriendly. Most are sharing a lesson they learned painfully when they were new to collecting.
The toothbrush just damaged the coin more. I'm glad the coin was not something valuable. There are very few ways a coin can be cleaned that a collector can't spot.
It doesn't matter how soft a brush you use to rub dirt around with on the surface of a coin you are still rubbing dirt on the surface which scratches it. It isn't necessarily the bristles that scratch it but the dirt that the bristles are rubbing around.