I’ve also used this thread and had the same experience. I just make my own thread now for welting and outsole stitching.
I was going to make a reference post for awl and thread sizes but I haven’t gotten around to it.
For now I will share this:
Ramie grade 8 thread:
3 ply for 7-9 spi
2 ply for 10-12 spi
TBH I am not a fan of using less then 3 strands because it makes it hard to get a nice long taper. However, ramie 8/1 is the easiest thread to find. If you can find some grade 12 or 16 thread then its nicer for high spi.
So what I use now is:
8/3 for 7-9 spi
16/5 for 10-12 spi
16/4 for 13-16 spi
I am not a fan of using a large amount of strands so like 6+. I always end up getting thread tangled and it becomes impossible to fix, also increases the chance to have small knots in the thread (its like fluff that comes from the spool, not from me). I am able to get a nice long 30-35 cm taper with 5 strands and this works well for the bristles I use.
This is all for leather soles where I make the holes using a square awl.
The awl sizes I use are the following:
80 mm for 7-8 spi
75 mm for 9-11 spi
65 mm for 14 spi
60 mm for 16 spi
For transparency, I have only done 7, 8, and 10 spi on completed shoes and I have done 11, 14, 16, spi on test pieces of welt and sole leather. The thread and awl sizes come from my own testing and some suggestions from William Efe Laborde and a retired Lobb outworker.
Awl sizes are a bit tricky since there can be small awls that have a large cutting surface and are thick along the shank, making them unsuitable for high spi work. Its always worth testing on scrap leather. It also gives you a good idea if your awl is strong enough for whatever sole leather you are using.
You basically want to use the smallest awl possible that won’t break easily.
I have no idea if this is useful for boots with a rubber sole but I figured I’d share in case.
For waxing I am a big fan of Starko tools wax. It preserves the color of the thread and smells amazing lol. One thing to be careful is if you use pitch glue to secure your bristle then there will be residue left that the rest of your thread will pick up, making your thread look greyish and black in some spots. I have also made my own wax but it always makes the thread look a bit yellowish.
In terms of polyester thread I have only used the vinymo double wax but when i asked Francis Waplinger he told me he uses Tiger for his outsole stitching. I’ve been meaning to try it for welting but its so expensive lol.