After reading into partial and experimenting over the past few days, I figured it out tonight and can repeat it (maybe a little too well). I made this account so that I can share my knowledge with you.
The difference for me was in how completely (and to a lesser extent quickly) I put my weight onto the noose. I had previously been pussyfooting around and easing my weight in, but the difference came when I relaxed all my weight into the noose all at once–it didn't hurt as much as I expected. I'll go into a little more detail for those who would like it:
Equipment
It's not as confidence inspiring as a doorway pull-up bar, which I consider the gold standard, but I have had no issue using one of these door hanging metal
coatracks as an anchor point. I weigh less than 165 lbs in case you're wondering. I've also been using a metal caribeaner and rope rated for what I believe was 180 lbs from Walmart. The caribeaner is in place of the knot on the noose end which makes things much simpler. I also pad the front of my neck with a face towel before applying the noose.
Experience
Since changing the key variable (complete, rather than tentative, release of weight onto noose), I have had three consecutive successful trials. My subjective experience was similar in all of them:
I started the timer on my phone and then released my weight with feet still in contact with the ground. In under eight seconds, I experienced the following: dimness of vision, feeling of weightlessness, mild tingling. Upon releasing myself, I had a hard time standing. I didn't experience anything unpleasant besides the minor discomfort of the weight of the noose on my neck, which was quickly (2-3 seconds) overshadowed by the darkness, tinglyness, and weightlessness.
Caution
My last trial is worth giving special note to. I followed the same procedure as the others but stayed just a second too long and nearly went over the edge. Of all my trials so far, this one quickly led to the dimmest vision, lightest and numbest body, foggiest thoughts, and greatest difficulty in standing. I remember looking at the timer and seeing 8 seconds when I staggered to my feet and struggled to remove the noose (although it's just a simple snap style caribeaner). Consciousness was very loose indeed.
A word of caution to those of you experimenting with partial: make sure you're ready to go and that you will not be found, even if you're just doing tests, as you may "succeed unexpectedly." There were others in my house who might've heard me and interrupted once the spasms started, and god knows what kind of situation I'd be in then.
Reflection
This trial gave me some things to consider. The primary emotion I felt after nearly losing my grip on the third trial was panic that my cohabitators would find me and get me locked away (need to experiment/attempt in a strictly empty house moving forward and also try to ensure that they will not be the ones finding me). The panic was exacerbated by the fact that I might've shared just a little too much with my doctor today–nothing to put my independence in jeopardy, but maybe enough to raise an eyebrow or two.
The secondary emotion I felt was the enhanced gravity and seriousness of the situation now that I really know what I'm doing and can ctb fairly reliably (knock on wood). I had some ambivalence, which was unexpected and needs to be examined before I fully let go.
Finally, I felt a mixture of satisfaction and relief knowing that I'd finally found a winning formula and that the choice is truly in my hands now. Partial is very peaceful and effective once you've dialed it in and is certainly my method of choice should I choose to proceed.
Happy to field any questions you may have.