Hi David, (and happy belated Thanksgiving! ) I don't know what I was thinking when I wrote about sticking needles in my hammers. I must have been asleep or something.... I've watched my technician use a needle but he didn't poke into the felts, he just used the tip to scrape the grooves a little bit - fluff them up to take off some or the brightness. I think your idea of a brass brush would work well too. Thank you very much for the instruction on how to do it.