Question
I am a big walking trigger point, and trying to stretch, release and strengthen my way back into health.  One of my biggest problems right now is a tight, tender psoas, which of course causes all sorts of flank and back pain as well as my anterior pelvic tilt.  (And if I understand what I've read, I'm one of the lucky 60% with a psoas minor, and that's excruciating too.)

All of the psoas streches I've seen require either an assistant, a bench, or the grip strength to hold onto your foot.  I've got none of those right now.  And the typical "lunge" stretch requires a lot of other muscle contraction; I can never relax into it.

Are there any psoas stretches that rely solely on body weight to perform the stretch?

Answer
You're right it is difficult to stretch the hip flexors adequately on your own. I've found the best way to stretch it solo is by using a physioball - 55cm if you're less than 5'5" and 65cm if your 5'6" or taller, and 75cm if you're 6'+. A decent ball should cost you less than $30 and it doesn't require a lot of space. You can lean into to it with the thigh on the same side your stretching (as if you were doing a lunge). The resistance gives you enough control to stretch the psoas major/minor while applying PIR stretching principles. Give it shot - it works great for me!