I would assume the way he is wording it, the pin holes are all located in an area about the size of a dime on the quarter panel, not that the holes are the size of a dime.

At any rate, closing up pin holes is a challenge. The very thin metal will often blow through before the hole can be filled. Personally, I would create a patch for the quarter panel that is a little larger then the rust damaged area and weld in the patch. it will be a better more permanent repair. Having access to both sides of the quarter panel will make welding in a small patch an all steel repair that can be done with very little or no filler at all. trying to braze the damaged area may create more problems then it will fix. Gene