I agree the car has to be clean but that is true no matter what you use.
I use the water blade, then I use my compressor with an air nozzles for places like the tail lights then finish up with a nice soft, 100% cotton towel then always Z6.
With care, the water blade saves a lot of time. I am, however about to buy an electric leaf blower. My wife already thinks I'm nuts so I might as well prove it. I have a two stroke, gas, leaf blower/vacuum/mulcher but it is a push around machine so I can't use it on the cars. When she sees me buying a leaf blower and wants to know why I need another one and I tell her because I can't pick up the one we have to use it on the cars she is going to fall down laughing.