So on the 14th of December I figured it out and learnt how to do it, and I hope my technique can help someone else get the hang of it if they’re having trouble. For context my “official” numbers are -4.25sph and -1.25cyl. Measured myself about -3.8sph -0.3cyl. I have a small amount of astigmatism in my eyes and I feel this may have aided the technique but it should work nonetheless.
For measuring the astigmatic axis I pulled up a Siemens star chart, one used to find astigmatism in photographic lenses, and combined it with a protractor around the edge.
I cover one eye. When I got one axis sharp and the rest in slight defocus I noticed that the blur in the out of focus area wasn’t constant. The interference between the out-of-focus lines created a sort of interference (moire?) that I saw fluctuate radially in and out of the centre.
After a short while of staring at it I noticed I could ever so slightly manipulate how close the blur/interference gets to the centre of the chart. I entertained this idea. The interference of the the out-of-focus lines created a sort of visual feedback to the brain as I tried to manipulate the lens in my eye. The in-focus lines caused by astigmatism presented a reference point to what all the out-of-focus lines ought to be and it became a game.
Eventually I got the blur to retreat closer and closer to the centre, and before long I was seeing all the lines sharp with equal boldness. I wasn’t able to hold it for long at this point, so I practised it a few times to eventually get the technique down.
A couple of days later I was listening to a podcast and looking out of the window at a tree without leaves. I was wearing my differentials of -3sph only, as I hadn’t ordered any normalized yet. At one point I stared at it and tried using the technique I had learnt. To my amazement I watched as the tree very slowly came into focus. Over one dioptre of blur cleared up and even the tiniest branches and the trees in the distance came into sharp focus.
The first time I did this it was quite jarring as it’s so dramatic and I’m technically not supposed to be able to see this clearly with just a -3sph correction. Today I can get it in focus much quicker and hold the focus for a little longer. If I get any double vision or ghosting during AF I can blink and it’s gone, though sometimes it takes a few tries.