I have completely stripped and re-'glassed three...yep...THREE kayaks. each time the result was better than the origional.

I have used various tools to grind off the old stuff. I start with what ever will do the most damage. I've used a right angle grinder with a course sanding disk, Ive used a belt sander and a random orbital sander. Start by grinding off 'glass and epoxy until 5-10% of the surface shows wood and the rest is a close to the wood as you dare.

Then use more controllable tools to fair the hull while removing the remainder of the epoxy down to clean bare wood. use a fairing board, to get every thing as smooth and fair as possible. use down to 80 or 120 grit sandpaper.

re-glass as you did the first time except that rather than using 'glass tape at the hull-deck joint, just overlapp the layers of 'glass at the joint.

there is no reason to expect the boat not to be BETTER than ever before. It is a pain in the neck but will save the boat from the wood stove.