In order to get your painted surfaces ready for machine polishing, or for applying coatings like Gyeon or Kamikaze, you must fully and properly prep the surfaces first. This can be accomplished through a combination of chemical decontamination by using products like Gyeon Iron, and mechanical decontamination by using detailing clay. These processes fully remove any embedded contaminants from the surface, and clean it much deeper than what you will achieve in a normal wash.
When preparing the surfaces of your car for waxes, sealants, or coatings, you'll want to make sure that there are no remnants of previous waxes, sealants, or polishing oils. This is accomplished by using a stripping agent like Gyeon Prep.