I cut and oil pieces of emery cloth to go over the end of a dowel and repeatedly "push" the emery patch through the bore from the breech. I am careful not to dull the sharp edge of the chamber at the breech. I think this is a bit more user friendly than using the drill, but the dowel and the size of the patch has to be carefully selected. A good coarse patch, well oiled, will last for many passes.