I find that a short piece of 12ga copper wire works well for me. Strip off the insulation and pound it into a tapered shape with a square cross section. About 3 minutes work with a hammer and hard, flat surface. If you want, you can "clean it up" by draw filing the flats. I taper it enough to fit in the touch hole a ways, and the edges on the square shape do a good job of cleaning fouling. Since it's copper, it doesn't harm the touch hole. After a bit of use, the softer copper will have rounded a bit from contact with the touch hole - it's a simple matter to clean it up again with draw filing. I bend a little loop in the back end and tie it to my horn strap.