Re: techniquies in street fights
In the modern army combatives program we recognize knife defenses and practice them somettimes. However not that often. Our philosophy is the winner of the fight is the guy whose buddy shows up with a gun first. Now that is contextual based on scenarios that soldiers face, (we never go in a situation alone). But still I think it is relevant to the civilian side as well somewhat.
I think it is important to always consider that your opponent may be armed, but to train for a knife fight as a sole focus of your training, IMHO, is not productive. Why? because I personally don't think it is realistic to face a knife wielding opponent who will present it so openly. Most knife attacks will be ambush attacks and you won't see it coming. Why do you want to give away the element of suprise if you are the attacker and truely mean to kill your opponent?
I think the way we train in aikido is good cause it always considers the knife attack as a possibility and attempts to limit the exposure you will have to a knife or other weapons.
Musashi is good, certainly you need to enter a fight in the proper frame of mind with no thought to winning or losing (mushin). It is also always better to avoid the fight if you can too. The ones you cannot avoid our ambushes where someone jumps you out of the blue. If they have a knife and have intent on using it, not much you can do but "stop, drop, and roll" (like the fire drill) and hope to minimize the damage.