This is an extremely interesting video. It seems that aiming a Tabor-style handgonne is not so difficult as one might think.
The earliest type of gunpowder, called “meal” or “serpentine” powder, was very fine, like flour. But it had a problem, as it was very hard to store and the component elements would separate from each other over time. Sometime before the turn of the 16th century, it was discovered that gunpowder could be “corned” into specks of consistent size to increase its power and longevity.
Meal powder burns slower than corned powder, giving the gunner a moment to aim with both hands, as demonstrated in the video.
The gunner also demonstrates the accuracy of his weapon at 11 yards. The grouping is not so bad at all, considering that he is shooting freehand with no sights and trying to keep steady during the long hangfire time.