shampoos

In my early days I tried Turtle wax's wash and wax shampoo and although it did impart a slight gloss on the paintwork, it also added white marks to the plastic trim in one fell swoop. Bumper trim, window surround and wing mirror housing support, plastic area around the wipers and air intakes...

Hi Please can anyone tell me the advantage (if any) of using PH Neutral car shampoos, have read somewhere that these are better prior to waxing. Many thanks