I use 1/16" lexan from US Plastics for my bills. I trace the pattern for the bill on the plastic film on the lexan, cut it out with tin snips about 1/8" from the line and sand it to final shape using a dremel with a sanding tool I made. Pics of the tool are below. You'll need aluminum flashing, closed-cell foam, #80 sandpaper and a dremel cut-off wheel mandrel. Trace a 1 1/4" circle on the flashing and the sandpaper (an empty spool of thread works well for this), cut out and drill or poke a hole in the exact center of each. Cut a smaller (7/8-1") circle out of the foam. Assemble by putting the sandpaper on the screw first, then the foam and then the flashing. Once you have the bill sanded to shape you can polish the edges by hand with finer sandpaper. The tool can also be used with #50-80 sandpaper for sanding lures.
Hope this helps.
Ben