I know some pet cleaners do a shedding soap. And they even take the under coat out to help shedding. I don't know how good it is.
There are some de-shedding shampoos out there, most of them contain a cosmetic-grade silicone that makes the hair slippery, thereby helping the dead hair slide out more easily. Compared to regular shampoo, I think the de-shedding shampoos *might* be marginally better for shedding, but I'm a professional groomer and I think the key to de-shedding is the HV dryer. It will blast out a ton of hair no matter what kind of shampoo you use.
For thickly coated dogs that are heavily molting, I will use a leave-in conditioning rinse which contains silicone. Just a capful of it to about two gallons of water, and I add about 2 cups of vinegar to the solution as well. I soak up the dog in this solution and let it dry without rinsing. The combination of vinegar and silicone helps the dog dry faster, gives the hair more "slip", thereby making brushing easier, cuts any remaining shampoo residue, and leaves a healthy pH level on the dog's skin that discourages yeast/bacteria/fungus. And it leaves the coat very shiny.
If you bathe your dog at home and don't have the luxury of an HV dryer, the de-shedding shampoo may make more of a difference and will be a heck of a lot easier than trying to soak the dog with a conditioning rinse.
If I didn't have access to professional grooming equipment, I'd never try to groom a GSD at home--I'd go to another groomer! In fact, I have taken my own dog to other groomers when I was between salons. Doing it at home can be back-breaking, time consuming work, and very messy. Having a groomer do it will be the best $50-60 bucks you've ever spent. I say this both as a groomer and a GSD owner!