Doesn't article 5 apply to official candidates?
I don't think Article 5 applies until they are actually invited and the invitation accepted.
However, my understanding (and someone with more international law experience can correct me if I am wrong) is that all the time consuming processes could, in theory, be bypassed if the NATO Council unanimously approves it. The summits that established the processes do not supersede the treaty as a whole - it isn't that they cannot admit anyone without the process. They just generally will not.