And yes, Oro was talking about that coffin jutsu.
No, he wasn't. The coffin justu(Edo Tensei) isn't something he developed on his own. The jutsu he is referring to is the one that Sandaime was surprised to see. The one he used to bind his own soul to that of a younger person. In episode 69, Sandaime recognizes the Edo Tensei. Orochimaru is planning to use his own technique to revive Tsunade's friends.