Miker Orlen can describe it better, but following his tips, I have done it several times. The dowel is slit on one end, about 2". Emery of the desired grit size is torn in a strip. The strip is inserted in the slit and wrapped round the dowel. I drive the dowel with my lathe but a drill motor would do the dame if the chuck is big enough. The wrap of emery needs to be fairly snug inside the bore. Run it in and out and it will remove a fair amount of roughness. It will remove more metal than the grit ball polishers that Brownells sells. Finish up with finer grit.
