I agree with the above, a car freshly out the paint shop will be covered in Swirls and trails. A body shop may polish a car for an hour with a harsh cutting compound and leave ti unrefined and covered in marks. Joe bloggs would never notice the swirls but to a detailer swirls are a sin lol. You will need to give it a decent polish. Its impossible to say with what as every paint is different and every paint has a different hardness. To buff a car properly should take the best part of a day........or two
I have always been told to leave a car for min 2 weeks after fresh paint before going near it with any polish.
A clay bar is for removing contaminants in the paint, a freshly painted car would have very few, but the clay will remove overspray.