Whats the point of the pre wash, why not just wash the car?
A. Basically, the pre wash will remove alot (id say at least 70-80% in my experience) of the road grime before i even start to touch the car with the mitt. The benefit of this is that i will not have to rub the dirt around the car, or transfer it to the bucket im working from, and then there is less chance of causing swirl marks.