I feel that the whole foam before wash is hoopla! As long as your car is not covered in mud, there is no reason to use a pressure washer. The two bucket soap/rinse method is the key to a safe, scratch free wash.
Heres washing with a foam gun.
Get out pressure washer,
Fill foam lance with expensive car wash,
connect hose to pressure washer,
plug in pressure washer,
foam car,
clean wheels,
wash with 2 bucket method,
pull in and dry,
put away pressure washer,roll up cord, roll up hose, then you are done.
I feel it adds way to many steps to wash the car to just to pre foam which really dosent do anything.
So as long as you do the 2 bucket method and you thoroughly rinse mit between panels you are definitely washing in an adequate way.
I also use a dedicated separate mitt and drying towel to do the side skirts, rear valance, bottom portion of the bumper and wheels as these are usually the dirtiest parts of the car.