Hi Ann.
I attach my girth points/straps with about a 6 cord of number 2 common hemp thread and roll my own and then use a glovers needle. Common hemp is not easy to source these days. I don't stitch with an awl but instead punch small holes about 1/2" apart for about 3 inches. The punch I use is a number zero so rather tiny but you can use an awl and make the holes as you go. I then stitch the strap to the webbing using a back stitch (one needle and not one on each end of the thread like saddle stitching). This is where you start at the second hole, go back to the first, then again use the 2nd hole and then the first. Go onto the 3rd hole, back to the second, then 4th, then 3rd etc. Get to the end of one side and you have one large length of thread that crosses over. Go to the 2nd hole from the end, then the last and continue to the end finishing with a double stitch in the last 2 holes. You can also use a cross over pattern of stitching and crossing over from side to side. This will give you a pattern on the back of the webbing sort of like cross lacing boots. If sourcing a good stout thread is a problem (and it need to be a good stout thread)I have used thin nylon para cord of about 23 kilogram breaking strain. This is about 1/2 the thickness of a good stout boot lace.
There is a fleeting glimps of the process starting at 6 min, 55 secs
If you get stuck, sing out.
Barra