Do I need to polish or paint correct before applying a ceramic coating?

For a true glass-bottle coating (CQUARTZ UK, Gyeon MOHS), yes — reviewers across r/AutoDetailing and r/Detailing repeatedly emphasize that prep (wash, decontamination, often a polish, then a panel wipe) is the single biggest predictor of how the coating performs and how long it lasts. Spray sealants are more forgiving and can be applied after a thorough wash.