I'd second that. He already roughly had an idea of how the process worked from Kayaba, so it wouldn't be beyond reason for him to "perfect" the method. Maybe by using his original NerveGear or something.

In any case, was I the only one who kinda effed up and misread the Yuuki's and thought just maybe Asuna and Yuuki were related? I started getting the feeling I was wrong and then this last episode confirmed it haha.