[CarsAndGuitars]

I've been using one - not for every wash - for only about a year, but have been serious about detailing my cars for many years. It is not a gimmick.

The idea is that some (most?) of the contaminants are loosened and carried away by the foam, rather than being rubbed into your clearcoat with your wash media. If your car is regularly washed (like mine are) there is not as much benefit since there is less dirt to damage your finish - but it can't hurt and is still just as fun. My process:

I use Meguiar's Hyper-wash, approx 3-4oz into the foam cannon reservoir.

First, rinse down the car, apply foam, starting with roof / hood and work down to vertical panels. Get full coverage including wheels. Allow the foam to dwell 5-10 minutes, depending on heat / sun (I am in S. Florida), then rinse thoroughly.

Here, I will either continue with my regular 2 bucket wash process or just reapply any remaining foam and agitate with a wash mitt and rinse.