When I worked at a veterinary hospital quite a few years ago, we used Massingill douche. It worked pretty well. But that was back in the late '70s. There may be better products available these days.

Having been sprayed twice myself, I can tell you that when the spray gets into hair (it permanently embeds itself in the protein of the hair, or fur, as the case may be), it never comes out completely. But since dogs shed their fur quite regularly, it shouldn't take more than a year or two for it to go away completely. Until then, the dog may smell a bit skunky when it gets wet.

Since I have very long hair, it took several years before people stopped sniffing around and looking puzzled whenever I entered a room with wet hair.