User blog comment:Kajune/Does Dean require demon blood for Michael to possess him?/@comment-27593090-20151230201510/@comment-27460953-20151230220250

You guys need to watch the episode again. This is the script "Sam....If you say yes to Lucifer and then fail...This fight will happen. And the collateral... It'll be immense. There's also the demon blood.

SAM What? What are you talking about?

CASTIEL To take in Lucifer, it would be more than you've ever drunk.

SAM But...Why?

CASTIEL It strengthens the vessel. Keeps it from exploding."

Castiel was obviously saying that Sam needed the blood just as Nick did. He is saying nothing about the blood helping him take control of his body.