I’ve fixed dozens of these. I don’t even attempt to remove the old glue, unless it interferes with the fitment. I like to use Devcon 5 minute epoxy for this repair. The trick is to make perfect dots of epoxy on brass strips that are just large enough to bond to the locomotive, but not ooze out. If you’re unsure, practice with some scrap card stock, etc, so you know how much spread you’re gonna get when you attach the piece. Really no need for clamps, gravity is your friend here, and no need to press hard, or you’ll put a bend in the thin brass that can become a fight …..Test fit all pieces and make whatever adjustments are necessary before gluing. The panels should lay on the engine as intended before the first drop of glue goes down.
Pat