Try spraying a light mist of denatured alcohol on a section, give it 3-4 minutes, and see if that improves the removal. Gradually work up the quantity and the time it sits until you find a technique that works well.

One thing you will want to avoid is having any shellac dripping onto any other bike parts (frame, rim, brake calipers, etc.). It's a real pain to remove. (Don't ask me how I know this.)