Gather materials from various sources. Find long push-broom handles with threaded screw heads. Collect ordinary household brooms with long natural straws. If you cannot find donated sources of handles or brooms, purchase them new from discount stores. The broom handles are available for purchase separately from broom heads, sparing some expense.
Cut a circle from a piece of scrap 3/4-inch plywood. Make the circle approximately 6 inches in diameter.
Drill 1/8-inch diameter holes along the edge of the plywood circle, in the center of the edge. Space the holes every 3/8 inches. Make the holes 1.5 inches deep.
Disassemble the household brooms to acquire a collection of long straws. The straws should be no less than 8 inches in length. Combine several straws together in a bunch that is approximately the same diameter as the holes drilled in the plywood circle. Bind the straws together tightly with wire 1.5 inches above the gathered end.
Fill a drill hole with hot melt glue. Insert a bundle of straws into the hole. Repeat, filling all the holes with straw bundles. If the arrangement looks sparse or patchy, drill more holes and insert more straws as needed.
Trim the straws with scissors until the chimney sweep broom head is approximately 16 inches in diameter from straw tip to straw tip.
Mount a threaded pipe flange on one side of the plywood circle. Choose a pipe flange that has a matching screw thread diameter to your push-broom handle screw head.
Assemble the handle and the broom head. Seal the handle to the pipe flange with a piece of black gaffer's tape.
Paint the plywood circle, the pipe flange, the broom handle, and the broom straws with flat black spray paint to simulate years of exposure to soot and creosote.
Create the rest of the chimney sweep's broom handles. Real chimney sweep brooms extend with more handles to make them long enough to reach all the way down through a chimney. Chimney sweeps traditionally carry a bundle of these extension handles over their shoulders with their broom. Cut wooden dowels of the same diameter as the broom handle and paint them to match. Make 8 to 10 of these extension handles for each broom.
Bundle the assembled broom and handles together with two leather straps or belts that are aged with "soot" as well.