Sorry for wrongly attributing the "blinding jab" to Fran -- don't remember where I saw it then, but the video was similar to what Fran produces so that was what contributed to my confusion.

The blinding jab was just a regular jab that was aimed at the eyes -- it covers any concurrent movement if the step is started shortly before contact or full extension (if the punch is too short to actually hit).

It blinds by blocking vision.

I also agree with Fran, it should NOT be thrown slow, nor "left out" there -- you must practice the movement to begin just as it blocks the eyes and to be complete by the time it uncovers them.

I have played with fine timing though, slowing it JUST A LITTLE near extension to gain a little more time.

That seems ok, depending on your opponent's reaction speed -- don't want someone to rip it off and hit you with it , nor to push it down and change your balance or get past your guard.

This last is very hard to perfect, i.e., a single punch that goes FAST-SLOW-FAST. If I do this I make no real attempt to "hit" the opponent, just to get it near his face and block his vision.

Never do I leave it "out there" even if I slow it a bit near the turn around point.