Ohh this.How did Sasuke teach his Susano'o to shoot a bow and arrow? Same thing.
I'm not saying it's unique; every Susano'o has been shown to move, and since Susano'o is a collection of the user's chakra, it can be assumed that the user can control how Susano'o moves. Therefore, Madara didn't have to teach Susano'o how to make handseals, he just made his Susano'o use handseals.Ohh this.
Madara's susanoo can use hand seals and sasuke's can shoot arrows so it must be a unique ability![]()