On a related matter, used Meguiars car wash on the weekend and did all the right things, washed in shade, one section at a time, used a sheet of running water to rinse the car not a spray, dried the car down afterwards etc. But I was not happy with the result as it finished up with a spotty residue on the paintwork. The only thing I can think off is that I made the washing solution too strong (Who knows what a fluid ounce is anyway?).

Any ideas