Our first is just out of this period and it really was pretty rough. It look us a month or so to come across the 5 S's and it made a world of difference.
We also somehow got very very lucky in that he didn't need to be transitioned out of the swaddle, he just grew to dislike it so one night we just stopped cold turkey and it was fine. We've had friends that have had to do the one arm in / one arm out, swaddle the legs, etc. and transition over days or weeks to get any sleep at all.
My son would always wriggle around until his hands were up next to his face (this is like 11 years ago). I started swaddling him in that position. We had an ultrasound picture that showed his hand in a similar position, so I guess it carried over.
We also somehow got very very lucky in that he didn't need to be transitioned out of the swaddle, he just grew to dislike it so one night we just stopped cold turkey and it was fine. We've had friends that have had to do the one arm in / one arm out, swaddle the legs, etc. and transition over days or weeks to get any sleep at all.