If they have in fact been on for 20 years, they are most likley cracked flaking..if thats the case, dull razor blades, heat, lots of time !!!!!!

The eraser wheels work pretty well. Only used them on cars to remove stripes though.

the eraser wheel works good on a car, not sure about gel coat. I have one looks like a angle grinder with a rubber cutting wheel. I paid 300 for it

eraser wheel, the only thing we use, cars or boats. I don't know exactly but we probably spin the drill around 1500 rpm. Always turn it into the vinyl, so your always catching an edge. www. offshoregroup.net