Yoga nidra (sleep meditation) has been quite helpful.
What really helped is also performing nervous system calming techniques not only at rest, but slowly when I walk around as well when I was able. Got the idea from Becca Kennedy who just posted this video: https://www.youtube.com/watch?v=XfZFtWx1YvM
The downside is that a lot of people are out to take your money when you read about this. I'm skeptical of brain retaining courses. I trust Deb Dana's books