First you should make sure you have the file that actually includes these gestures, as the OS 5.9 releases did not include them (I think I saw somewhere that you already grabbed the newer version though).
So that’s first.
Stab is a forward motion ending in an impact at the tip, so literally stabbing a wall for example.
Thrust is a bit trickier, where it is a motion that starts from a complete stand still then a forward “stabbing” motion but no impact required. If you end the motion with a sudden stopping jerk, you may trigger a false clash, which would trigger a stab instead, so while practicing I suggest distinct sounds or look for a stab blade animation to clarify which you are triggering. The beginning of the motion is where I find it triggers, and sometimes I find it helpful to “almost” pull backwards a touch first, but more a mental cue than actually pulling backward if that makes sense.
The speed at which you start, (in my mind when I do it) is similar to what you’d do if you banged your elbow on something and hit your funny bone, sort of a sudden knee-jerk reaction, then a smooth follow through on the forward thrust extension of your arm. (mouthful, huh?!)
Push is the most difficult IMO, and it uses translation, which in itself is difficult to make work in the code . Holding the saber pointing up for example, you would push it laterally away from you like a short punching motion. Sometimes I find more of a “jab” motion with some pronation helps, sometimes I
get it inadvertently when just clashing the hilt against my other hand…it’s tough. There’s also FORCE_PUSH_LENGTH that can adjust the sensitivity. 1 = shortest distance to trigger (easiest for some), 10 = longest motion required to trigger.
Once you “get” these with some practice, you should be able to do them on command, but it does take practice.