how bad is the red paint underneath all of the artwork? Did they just brush that on too? If so, you've got plenty of sanding to do I would think, if you are shooting for a smooth finish that is. I was gonna suggest chemical stripping, but that would probably be a toxic nightmare given how much has to come off. I've done small sections before, but never a whole car. That stuff really works, but it is really nasty, to your skin, to the air (vapors are brutal), and the mess it makes getting all the paint off. It might take longer, but I'd stay with the sanding.