Absolute game-changer for me was learning about "position of true rest" and making time to get as close to that as possible for even a few minutes a day. For me it's a soft seat, soft reclined back, feet up, arms supported, head supported and leaning back. I watch TV and read like this now. It helps even if imperfect but it's much better if all the cushions are exactly perfect, so learning how to tell and then adjust is hard.
Trying to really not do things that make it worse unless they're very worth it. eg I go to the office as little as possible now and I let work buy me a fancy chair, in my spare time I try and go to events where I can move around often and where the seating options are supportive, I try and carry an absolute minimum (light shoes, light coat, no bag unless it's really necessary). A metal-framed rucksack with hip straps if I really need to carry something. Stabilising myself is a big difficulty for me so if there's seating for people who need it, like on the train, I admit to myself that I need it and I ask for it. The hardest part of all this is accepting my needs and valuing my wellbeing over what I think I "should" be able to do.
Physio with someone who understands my condition and listens when I say something is too hard even if it sounds easy. Stretches and fascial release and foam rollers.
Qigong and walking and not "working out". Wiggling in ways that probably look weird.
Making sure I'm warm enough.
I went to an osteopath who specialises in difficult cases and she taught me. I think the idea is that your muscles and joints are in as relaxed a position as possible, not working to stay put. It can also be referred to as a neutral position.
I struggled to find anything too but there's this very short piece
https://dorsetpain.org.uk/SiteUploads/45/Uploads/B8.2%20True%20Rest.pdf