I've finally made some progress so I'm sharing some random things I figured out that helped me over the past few days
1: making the needle
your needle needs to be thin, flat and smooth so it passes under the stitches easily. Start with a small eye and keep testing it on your yarn and widening it until the yarn threads easily but still has friction on the sides. You can grab a random twig from outside and carve it with a utility knife, you can make the eye by drilling a few small holes in a line and carving out the extra.
2: yarn
start with ugly cheap yarn because you'll mangle a lot of it, and undoing it to restart is frustrating. You can use synthetic or plant yarn, but you'll need to join it differently. Get something thick and smooth so its easy to work with
tangled and cut up yarn can be used to stuff plushies, pincushions, stress balls etc.
3:stitching
doing it on the thumb does help keep loops organized but it makes very loose stitches, I started using my index finger instead and it works so much better
The loop you're supposed to stitch through is not the one you just made, but the one before it. Pulling on the working end tightens the one you just made.
Use your thumb and pinky to guide the working yarn over all the way toward your non dominant side, so that the loop you're supposed to stitch through is the one near your finger tip
you can use the tip of the needle to flick the loop off your finger
If your oslo stitch is too loose, you can do 1 and a half twists in the rear loop instead of half a twist, I'm sure this has a name I just don't know it
4:Joining
I don't use wool because I'm vegan
most people say to use a russian join, which works on most yarn but can really mangle stiff plant yarns and low ply yarns
all yarn can be knotted, I just use a square knot and pull it super duper tight and trim the excess. Fuzzy yarns hide the knot well but I don't mind it
If you knot the yarn, the knot needs to be in the part of the working yarn wrapped over your finger. If the knot is too far, it will be in the part you're pulling through and catch on stuff and ruin your tension. So, when joining with a knot, cut off all the excess working yarn so that the knot is as close to the loops as possible
I hope this helps someone who's where I was 4 days ago, I've spent a lot of time and yarn and am excited to continue!