the women in the video does not swaddle as tight as dr. karp because when he does it the last piece comes all the way around the baby's chest and back and is tucked in somewhere on the chest of the baby (hope that makes sense). dr. karp says this last piece holds the whole swaddle together.
Dr Harvey Karp saved my sanity. You should get his book from the library called "the happiest baby on the block". It's an easy read even though I found it a bit too wordy. He discusses the 5 s's (shusshing, swaddling, swinging, sucking and i can't for the life of me remember the other one). Anyway, the swaddling was a lifesaver. The video that was suggested by the other post is way too loose for karp.
I used it (swaddle) because ds cried soooo much, had reflux. Along with white noise (we use an old radio tuned to a non-station), the swaddle was a godsend. Ds would immediately take a breath from all that crying and somewhat relax.
Ds is 5 months and I use the white noise everytime he naps and at night. It drowns out any noise, i.e. phone, doorbell, footsteps.
Ds also did a lot of napping in my cuddlywrap. I didn't get much done but you could go for a lot of walks. he loved it. He'd nap in it for up to 4 hours at a time.
I would also recommend taking out Karp's "happiest toddler on the block" from the library, too. Also a fast read.