The technique we used is, the person in the water (wearing a vest) positions themself midship with their back to the gunwale. The person in the boat grabs the vest above the shoulder and pulls until the person in the water is sitting on the gunwale. As the person in the water is lifted higher, he/she can assist the lift lift by placing their hands on the gunwale and pushing until in the seated position.
Buoyancy goes a long way in assisting the lift, so you can lift a relatively large person that you would not otherwise be able to lift on dry land.
I always keep a hand on the person to stabilize them while they rotate and enter the boat.
I am really not a fan of attaching anything to the side of the boat.
Cheers,
Joe