I haven't done holsters but when I worked in a saddle shop, a jerk needle was our secret weapon for hand-stitching in difficult places where the machines couldn't get to, or that required a bit of extra care or manipulation. The lack of info on them is curious to me, and the thread here doesn't quite satisfy your query. I have used machines, double and single hand needles, speedy-stitchers, etc. I find a jerk needle to be much more effective than a speedy-stitcher, a tool I do not particularly like at all. The reason for that is that the jerk needle can perform the lock-stitch and then be moved out of the way so that your hands can set the stitch tight and proper. A speedy-stitcher isn't nearly as speedy and the sharp needle is always in the way. Don't use the jerk-needle as a hole-maker. Pre-punch your holes with whatever means you have and then use the jerk-needle. On the welt of a saddle seat, we would mark the holes with a hole marker and then use a drill to go through all the layers, then use a jerk needle in an awl haft. Having tried the other methods, a jerk needle can be much faster with excellent stitches than the other options once you get your technique right. As for finishing a row and setting the stitch, it's just like any other method where you need to pull a little loop through, make a little knot, set the stitch and knot back in the middle of your material, cut the ends, and melt any remnants.
I'm not sure if that is entirely clear, perhaps I should make a video on the technique someday. However, I hold the tool in high regard and it just doesn't seem to be utilized to its potential for some reason.