Ok, you need a drill, a strong metal or wooden rod small enough to fit in the drill chuck (i used a paint whisk), some duct tape, gloves and sand paper (i used 80 then 120 grit).
First remove the rubber rings, then wrap the tape around the rod until its just smaller than the inside diameter of the handle, then slide the handle down the rod until it sits snugly over the tape like this.
Screw in the grub screws into the tape to secure the handle on the rod and put the rod in the drill.
Now set the drill on the fastest setting, put a glove/ gloves on, take a piece of sand paper in one hand and wrap it around the handle. Start slowly at first (it will get hot so be careful) and build up to a reasonable speed. Moving the handle back and forth through the sand paper while spinning will cut quicker and not leave any deeper rings scored into the handle. Moving it back and forth slowly while spinning fast will leave the brushed pattern all in the same direction instead of criss crossed sanding marks everywhere. Keep going until all the corrosion has been sanded off, you will need to stop several times as it will get very hot! I used 80 grit then 120 grit to leave it with a brushed look.
If you wanted to polish it just repeat the sanding process with finer and finer sand paper and eventually a cloth and some autosol or similar.
