When I burnish leather on the shoes or bags I make, or occasionally wood, I use a flat bone folder where the corners have been rounded a bit. I am assuming you are burnishing wood ( being right there on the uptake) so you might try flattening,rounding the edges and polishing the antler or just going to bone. The flatter surface does a more uniform and smoother job with less work, but antler may be too soft on the inside. You can pick these babies up at any leather craft store
The best burnisher for surface area, though, has proven to be a simple glass jar. Right off the grocery shelf, making sure it does not have any raised surfaces. I will wear a work glove because I am a nervous nellie; apple sauce or mayo make outstanding, uniform burnishers.
My old Cordwainer Master used to also take a piece of glass, score it, snap it and use it as a scraper on sole leather and I have tried that on wood. I've never had a scraping or shaving tool more efficient than that.
Don't shoot yore eye out, kid
The Capgun Kid