fine tuning handle

I used a pre-made handle, now that I've used the rod a couple of times I want to sand down the handle in order to better fit my grip. Other than spending $$$ on a lathe, any suggestions on how to go about it?

I've built many rod grips using coarse-tooth files for most of the shaping. But you're probably close enough to the dimensions you want that you can do it with several grades of sandpaper, coarse to extra fine. Wrap sandpaper around a thickish paperback, lay the butt section across your lap, and start sanding, turning the rod every few strokes. Dust or blow the loose cork dust off and check how the grip feels frequently, since you can't put it back. Fine emery paper gives me a smoother handle than sandpaper.