Cut out a curved template for a 2 ,2 and half , and 3 inch fades. Lay it down on the bow, and scribe the lines. Cut with the rasp of your choice to your template lines using a finer rasps as you go, and finish off with rough to fine sand paper. Practice on a scrap piece of wood. Soon you will be able to cut a nice fade with out the template, and if you are not sure of your self you always have the template to check your work as you go.