Ok I´ll try alternate picking now, it also seems to be logical, because with sweeping i also thought it sounds too weak if i listen to it.

To Trent J Liberty:
Yes, the kid in the movie(played by Ralph Macchio, the karate kid actor) uses his finger picking for this solo, but it was made by steve vai in the studio. I was just wondering how did they manage that you don´t see that it´s not ralph macchio who plays this.