When I was a kid, my brother used to do a weird method. He used to lay the chicken on its chest, legs behind it and head pointed straight along the ground. then he would take a twig and run it down the head, along the comb and down the beak to the ground, continueing out from the beak he would scrape a line in the dirt, all this is done very slowly. After a few seconds, he would release the bird very carefully. They would lay there for a few seconds before they blinked and stood up. I never put them on thier back, I believe that puts pressure on their lungs from their innards squishing them.