Every wax has its method of application, some waxes need to haze up before getting removed while some are WOWO(wax on wax off) that dont need hazing up. For carnauba waxes it is recommended to do panel by panel. Why?. They have a lower melting point so especially with the coming summer where temperatures are pretty high, if you do the whole car and then remove the wax, then well you'll be having a bad time:
1) First you'll be using excessive force in removing the wax causing swirls on the car.
2) You'll notice that the wax will be removing marks on the paint. Although its not such a big problem and not that noticeable, for a detailer it is irritating.
3) The major problem, due to dusty nature of our environment, when you will remove wax after waxing whole, dust might have settled on the car resulting in swirls when you remove.
Even after washing car you'll notice dust settling on the car pretty easily.
Some waxes can be applied in direct sunlight too for e.g Meg UW.
