Jake,
I'm not Al, and I'm not an expert or even an "old hand" at stitching the outsole by hand but I have done it and I remember some tidbits of advice that I received along the way...which may or may not help. Maybe if I flub it bad enough or give such ignorant advice, someone who really is everyday familiar with the technique will step in and correct us both.
Anyway here's a shot...
I wet my outsole with a spritz bottle just before stitching and just along the perimeter where I am going to cut my channel in from the edge and stitch.
I used a "square awl" all the way around. Didn't change awls or even awls sizes.
I used Teklon thread but you could use linen easily, and make the waxed ends up yourself. I bristled mine as usual. But I think you want a white wax for this job. Supposedly an odd number of threads will stay round and an even number of threads will lay flat. Isn't that right?...anybody?
I kind of like the idea of a real shallow channel in the welt but I've been told that that practice was frowned upon as indicative of amateur work. Despite that, I've seen some high end, semi-custom shoes, with a welt channel.
I used a stitch marker to space my stitches--10-12 to the inch--but I've been told that a "fudge wheel" works as well or better. And there's a tricky little technique involving a strip of leather fixed in close to the vamp that can help you keep your stitches an even distance from the vamp. But I won't try to explain that, as I've never even had the chance to fiddle with it.
As for the "jigger"...essentially it is a tool that is moved back and forth (Salaman). But, in this context, it probably applies to that little "ridge" in some of the old forepart irons that leaves a very neat and slight "step" on the top of the outsole/welt edge. This is suppose to make the outsole look thinner. In modern work and in more modern tools--even hand irons--the "jigger step" has probably been replaced by the top edge "wire."(just speculation)
I hope this helps...I know the query was not addressed to me and my responses may be more like "the blind leading the blind." But for what it's worth...
Tight Stitches
DWFII--Member HCC
frommer@bootmaker.com
http://www.bootmaker.com