I use my foam gun when the car is really dirty as a pre-soak to loosen up the heavy grime. I end up filling the entire foamer bottle up with shampoo solution, and just spray foam on the car until I run out. I can usually hose off a good amount of dirt before even touching the mitt to the car (which is really helpful preventing swirls on the soft black Honda paint).

 

I was just messing around.. The car looks great.

 

For me, the biggest benefit of the foam gun was in cleaning the wheels. It really made is SO easy. However, the foam would run off my car too quickly to see much of a benefit on the paint. I did find the more soap I used the thicker the foam, but the thicker I made the foam the more difficult a time the gun seemed to have dispersing it over the car. Plus, I really didn't want to use tons and tons of soap every time I wash the car as all I have on hand right now is the good stuff. So, I'm hoping the foam cannon will be more efficient.