Its called optimum no rinse (ONR)
basically you can wash an entire car with about 1 and 1/2 to 2 gallons of water.
i use 2 full capfulls (liberal capfulls) to that water ratio.
takes about 1 and 1/2 to wash my p5.
Its just like a regular car wash. There is no hose pre rinse, and the solution doesnt need to be rinsed off. Just wiped on with your wash media (mitts, grout sponges, etc) and dried off with a waffle weave.
My process uses the 2 bucket method as well. ONR basically encapsulates the dirt safely, and is allowed to be wiped off while keeping marring to a minimum.
ONR is a great product. It can be diluted to clay lube, quick detailer, interior cleaner, pad conditioner etc. One of my favorite uses is as a glass cleaner. I have streak free windows when diluted to 1 liberal capful to 32oz. I spray on, wipe with one MF, and dry with another.
I highly recommend this product