u just need to be a little expert for that ... its very easy to check wheather its paint or orginal ... i mean there is a difference .. there is no such formula .. khudi andaza ho jata hey ...
mostly old cars like more than 7 years old if u found the body paint in very gud condition then most of the time its painted not original ...
and u can check by taking the carpets off from the trunk and frm inside body under hood if its welded frm some where then for sure its painted
painted body gets scratch very quick but original paint dont get scratches too quick ...
just check the car if its old and in very gud condition then mostly its painted thts the simple way ..