Note: Teräs Käsi, being effectively a way to simulate physical and some mental Force Powers for non-Force Sensitives, is one of those vague and nebulously all-encompassing skillsets in the lore that necessitates it be rare, and we either must put hard limits on it that makes it less powerful than its lore implies or give it some measure of that broad power while making it cost more in turn. The easier path is the former. As presented below, I've gone that route, and am leaving the bulk of its insane implications as just fluff that shouldn't throw off in-character balance /too/ much.
Teräs Käsi is both a Rare and a Mentored expertise - this is represents that it is not only a rare practice in the galaxy, but also that it must be continually taught by a mentor to be learned at a higher level.
What is Teräs Käsi?
No Points: You cannot perform Teräs Käsi.
1 Point: You have begun to learn the art of the Steel Hand. Your strength, speed, and agility in combat are greater than a normal person's, but not by a lot. Armed or not, you can hold your own against skilled opponents and small groups. The more advanced aspects of the art still elude you.
2 Points: You have started to cultivate your mental control of your body more finely. You are able to anticipate incoming strikes surprisingly well, cause damage to even armored opponents, and have become proficiently acrobatic. You are alarmingly quick and powerful, more than your body should normally be. You are now able to achieve basic healing trances to recover from minor injuries, stop bleeding, and slow the progress of poisons, or go for a time without food or water. You can harden your physical form sufficiently to block otherwise terrifying weaponry with just your own body - this is dangerous and risky to do, and you cannot block lightsabers in this way.
3 Points: You are a blur. Your strikes are powerful enough to not just damage armored opponents but to damage the armor itself, potentially breaking it outright, and your reflexes are nothing short of incredible. Your trances are more potent in healing yourself, and you could go for days or weeks without food or water in such a trance, even resisting disease. You can control your descent when falling - not enough to slow yourself down, but enough to avoid obstacles.
3☆ (Mastery): You are a true Teräs Käsi Master. Armor means nothing to you when your fists alone can cave in durasteel and you can maneuver with such speed and precision to deliver strikes to an opponent's weakpoints that you are little more than a blur to their eyes. Your trances are potent, allowing you to heal yourself of significant injuries and stall poison and disease entirely, going for months, years even, in such a state. You cannot regenerate limbs this way. If you are Force Sensitive, you can achieve even greater feats such as the Far Strike - punching a target with focused air pressure from a distance.