We use the DIY dog wash at one of the pet stores. So far so good. Everything looked pretty clean in the wash room each time we have used it. I bring my own shampoo and towels. $10 for 20 minutes. I do have to bring my 15-year-old with me - Indie still struggles quite a bit - they are always much stronger than they look. There is hair and water everywhere when we finish. We clean up what we can. They also have squeegies in the room to dry the wet floor.
The only downside - I didn't go in the winter since I towel dry her instead of using the blow dryer. She has been kind of itchy and I didn't want to dry her skin out even more.
I think I have an alternative plan going forward. Tractor Supply sells these huge oblong tubs that have a drain at the bottom of the side where you can hook up a hose. They are about $70. I have a hot and cold water connection in the corner of my basement and room to keep one of these tubs there. I could drain it with a hose into the floor drain. Getting her in and out safely is the next problem to solve since they are almost waist high.
Copper (Lab mix) 2001-
Indie (GSD) 2013-
Spike (Rott mix) ?-2012 RIP big boy
Charlie (meow) 2000-
Puma (meow) 2010-
Nitro (meow) 2010-