I don't think he's really learned the 4-tails cloak. They said before that his seal's weakening as time goes by, so now he's got access, that's all.

And the key to unleashing it is his emotions. It works when he's pissed or when he's about to die. From what the anime seems to show, when he's emotionally unstable, he's also in tight situations, and unconsciously asks for more power, letting the Kyuubi leak its power. He's got to keep a level enough head to then consciously push it back.

So really, I don't think he learned how to use, or access the 4 tails at all.