wash when there is excesive dirt on the car. wax when rain drops don't bead on paint any more.
i use touchless wash. not the most thorough but will never scratch your clear coat.
btw bmw paint is softer than tofu!
E92 M3 DCT - AiM EVO4 Data Logger / AiM SmartyCam HD / KW Competition 2-Way / OMP ARS Racing Seats / Brembo GT 365 / Pagid Yellow RS-29 / Rear Seats Delete