PRIMUS is a pre-wash cleaner that you do not need a snow foam lance or pressure washer to use.
Just spray on, leave to dwell and then rinse off.
Use it to help remove as much dirt and grime as possible before touching your paintwork with your shampoo and wash mitt.
It will break apart oily films; start to dissolve grime and lift and loosen the larger particles of dirt and grit that might be stuck on your paintwork. Rinsing off with water will take the vast majority of contaminants with it. Which means you are a lot less likely to inflict damage when it comes to shampooing.