the first thing you need to work out is what is the paint?

i had a job a few months ago.where a company sprayed a running track and covered some cars in the car park with orange overspray.

clay didnt touch it.machine polishing didnt really work.

i found the best way was to wash the car first with standard thinners (cheacked for smart repairs before hand) then machine polish with a medium cut compound.

but each paint overspray is different