I used a steel wall-paper stripper and a flat bladed screwdriver. It did take me a couple of hours per drive, but worth it I think.
I just have a starboard prop diffuser ring to fit and then the boat is almost ready to go back in the water, just the port trim-tab ram needs to be replaced. The sharp eyed will have picked this up as I haven't anti-fouled it yet. I'm looking forward to seeing how fast she will go with everything ship-shape, clean oil, new belts, filters, etc. etc.
I'm hoping that next year there will be far fewer barnacles at the end of the year