I just saw something very silly by someone who shall remain nameless because I’m gonna criticize him. He’s a self-defense instructor and was teaching what to do when somebody pulls a knife on you. His technique completely ignored 3 things: first, that nobody leaves a knife out there for you to grab; second, that if you do grab the knife-hand, the attacker will try to pull away and if you hold on you will either get your hand cut or get stabbed, and three, his technique moved to the “hot” side–the side where the attacker’s other hand can strike you.
Moral: many of the techniques “experts” teach can expose you to even more danger. Be careful of both the techniques and of the “experts”.