some jackass painted something and over sprayed my Z

Bulletz4break

This ^^^^ Your risking scratching the hell out of your paint with clay, especially if you're unfamiliar with what you're doing. Being professional detailer, after claying a vehicle I always machine polish because claying will almost always introduce some micro marring into the paint. You having a white vehicle will not notice it nearly as much as you would on a darker color, but depending on the type of paint that is all over your car could make it a nightmare to remove.