We can talk about the different ways of sealing a bijuu. But I'm very interested in the following. Yondaime Hokage sealed the Kyuubi just like the Third did. There was a battle between him and the Kyuubi. That makes sense and is believable.

But, HOW did chiyo put the Shukaku inside Gaara? It's not like Shukaku sits there and waits there. Maybe they took the Shukaku from someone else.