I think there are going to be many methods found and discussed which will hopefully give each us some insight into the best ways to use the foam gun.
First when I did my review of it, I continued to use my two buckets, three mitts, a wheel brush and a tire brush. It's a tool and can be manipulated into doing what you want within reason. Here's how I got my results:
1) filled 2 buckets 1 with 1/2 of Super Slick & Suds added three mitts into the foam to soak....
2) rinsed off the Tahoe with just plain water
3) added 2 ounces of Super Slick & Suds into the empty container
4) put it on the smallest brass hole ...pulled the trigger and out came suds...lots of them

I considered this step a pre-wash and made sure the soap was everywhere, sort of like Nourah's review, but soapier.
5) then normal washing with my chenille cotton wash mitts (with a pair of 6 year olds)
6) disconnected the foam gun and rinsed the vehicle
My Thoughts:
I think everyone will have differences seen from soap product to soap product as far as suds, detergent content and slickness go and also the factors of dilution and minerals in the water (hard water) will all be variables to yield different results even with similar technique.
It can't be expected that this is just miracle product that will protect finishes:no: it's a tool to be used in conjunction with other tools, to achieve better results.