I use a much smaller file to drawfile a round barrel than an octagonal one. When I'm satisfied I have all of the machining marks off the round barrel, I use abrasive cloth in 180, 220, 320 grit backed by a pine block that has been prepared to fit over the round barrel...cut a rough trough in a block of pine and then put sand paper upsidedown on the barrel, and slide the wood over the paper to make it the same profile as the barrel. Always go lengthwise on the round barrel, or the octagonal part for that matter. For a matte brown, 180 or 220 grit is lots, but for a polished smooth look, I take the barrel to 400 grit. Probably overkill.