What paint to use for the sphere?

Hi Ben, Thanks for your Question, as you are restoring a 26" I assume is a later plastic Keracolor, but it could be old of the last GRP models as they made the 26" in both, with the plastic being more common. You can use any car spray paint, however we find using a spray paint design for plastic works best, painting spheres isn't easy & you need to ensure the temperature of the room is correct & well ventilated, and you have a good key on the case for the paint to stick too. Good luck with the restoration, and we look forward to seeing some pictures. Regards John