Knife fighting?
I believe that everything should be simple.
I had an interest in knife fighting a few years ago.
We have no shortage of disabled veterans here in Florida, and I hired a combat veteran marine to teach me about the intricacies of using a ka-bar, which is my preferred blade. He drilled me for hours on how to approach quietly from behind, how to target the femoral arteries, etc..
People seem to want to assume the the far east martial arts techniques are...somehow...superior to USMC hand-to-hand combat training, but they leave out an important point: Marine knife techniques are predicated on the idea that the combatant is weighed down with a pack, rifle, and web gear.
I discovered that trying many of the Eastern techniques with a pack, equipment, rifle, etc. won't work as well and will throw you off balance (although they work very well if you are unencumbered).
A good way to practice is to use fake knives and fake blood against a mannequin, and graduate to a sparring partner. A party supply store that carries costumes for Halloween can be a good source of fake blood.
Practice with a full backpack and heavy clothing. Also, practice with multiple assailants.
If a fight seems imminent, conceal a backup blade in the environment if it can be done without being noticed, so if you're taken captive and searched...the blade can be retrieved later if your captors relax.
Don't follow any rules in an actual knife fight. If you can end the fight by taking a hostage, then do so.
If you are wounded and an artery is spraying, aim the blood at your opponents eyes to create a temporary loss of vision that you should exploit before you pass out.
And so on.
Disabled marines are a great source of information and training if you can hire them.