Very interesting idea. antinn and I were reviewing a paper he found comparing the effectiveness of a grounded brush vs ionization vs both together in neutralizing static on plastic film. The brush was not touching the film but 1/16th of an inch off. It did lower the charge but it was not as effective as ionization. However they worked best together. So, a grounded metal bar or rod suspended over the record will work but it would have to be very close, so close that the slightest warp would stop the entire show.
What you are doing with your grounded brush is fine. I recommend wiring these brushes to ground all the time as just holding them does not do much good. The thing is you do not want to use it on a spinning record. Move the record under the brush by hand slowly. None of these brushes will get deep down into the groove. They will only remove surface dust. If the record starts out clean and your record hygiene and environment are good this should be all you need to do.
What you are doing with your grounded brush is fine. I recommend wiring these brushes to ground all the time as just holding them does not do much good. The thing is you do not want to use it on a spinning record. Move the record under the brush by hand slowly. None of these brushes will get deep down into the groove. They will only remove surface dust. If the record starts out clean and your record hygiene and environment are good this should be all you need to do.