Hydrosurge Rapid Bath????

You can make your own hydrosurge (the recirculating kind) using a sump pump and a couple other things, I forget what they were, but it was pretty simple to make. (a friend explained it to me a while back) It comes out to be around $100 but you can use whatever shampoo you need. I haven't used the rapid bath thing, but in the commercials it looks like the water pressure is pretty low on it and you need enough pressure to get through that thick GSD coat.

Bet tip I ever got on this subject was about the issue of "flow restrictors" inside every shower head sold in America. They are a water-saving feature, and for everyday human showers are probably a good conservation idea. But restricted flow makes giving dogs a bath difficult---it takes forever to wet and rinse a double-coated dog with no water pressure.

So--- go to a plumbing supply store and ask the guy to show a you handheld shower that has a flow restrictor that you can remove. Some of them come with flow restrictors that you can "remove for cleaning" (wink wink). Without that restrictor, a hand shower in your tub has full water pressure--it's a strong as the force of a garden hose, but with warm water, in the comfort of your tub.

I bought this one online and love it. I use it just for washing dogs. Note it has a removable flow restrictor. It comes with simple instructions on how to unscrew the thing, pop out a little plastic disk inside, and presto--full force hand shower.

http://www.highpressureshowerheads.com/high-pressure-shower-head-rain.htm#HH