With a little work adn patience you can easily do this yourself. You will need a pliers, a straight edge, a heat gun/ hair dryer, masking tape and various grit sandpapers.... Start by taping of the sections of cork you want to keep to avoid cutting/sanding them. Allow yourself 1 or 2 rings to work with in the sanding process. For the rings that you want to remove, slice them parallel to the blank as deep as you can without touching the blank. Do this on at least two sides of the cork, 3 or 4 cuts is better/easier for the next step. After the cork has been cut, use the pliers to grip the cork and twit it off in chunks, again be careful not to touch the blank itself while removing the cork. Once the cork is removed, there will/ should be epoxy on the blank still. Use the heat gun/ hair dryer to warm the epoxy to soften it up and again use the straight edge to back drag the epoxy to remove it from the blank, or you may be able to use a thumbnail to scrape it off as well. Some finish/paint might be removed during this step, but that is normal. Once all of the epoxy is removed form the blank, tape off the newly uncovered part of the blank to avoid sanding/scratching it while sanding the edges of the remaining rings to the taper that you desire. If you want you can paint the area of the blank that you uncovered or add some "bling" to the area to cover any scratches/scuffs that may have happened in the cork/epoxy removal steps. It won't make the rod fish any better by painting or adding bling, but may make it look nicer...
Hopefully this helps.