I mentioned above that I have my own shearing technique for a sokuto (foot blade). It's a bit off the traditional beaten path, but it's a good one.
Say you're being accosted by someone (rapist, thug, drunk) and you want to get away from them. And they've grabbed you. Well...
Extend your foot blade out and place it on the shin just below the knee joint. If the person is in front, you might try placing your right foot on their left shin, or left-on-right. That way you're away from their muscle tissue, and touching nothing but skin over bone.
Then... stomp down their shin with a shearing motion of your foot blade. If you're at the right angle (say you did this with them grabbing from behind), you can finish the shear with a stomp down on the top of their foot where all those bones are. Put all your body weight on the stomp.
Practice this GENTLY with bare feet. Then practice it EVEN MORE GENTLY with shoes on. You'll soon discover for yourself how this can work, and what angles work best.
With a shoe on, the inside blade of your shoe works just as well. This is where having an instep front kick comes in valuable. Different angles create different possibilities, and suggest different parts of your shoe edge for point of contact. Only the (lack of) sickness of your sadistic mind will hold you back.
I was about to say you don't need to do any follow-up if you do this with gusto. But that wouldn't be any fun...

- Bill