I have had a little success this morning with ds on his back (can't easily put him on his side as he is swaddled in a miracle blanket). I find that if I put my hand on his left hip and kind of push in towards his body he seems to respond okay. Really it is a kind of jiggle. I wonder how much the movement is what soothes them. Anyway, I have managed to get ds fall asleep in his crib for the last 3 sleeps doing it this way (I'm sure it mostly has to do with timing and darkness, etc., but I will go with this). Granted i am pushing a bit long (even while he is quiet and drifting off), but I figure if it eases the transition to falling asleep in the crib I will go with it and gradually reduce it over time.
This is our first string of successes so I think it might be the jiggling aspect that works? On their side I would imagine you would push towards his head, otherwise he might get tippy iykwim? However, I figure if you find something that works with you go for it!