Sam is a horse that chooses to spook to get out of doing something that may not be what he wants to do. He'd rather act like a big baby than try. So, I ask him nicely to step on the tarp. No pressure on his halter, just a suggestion to move forward. If he side steps, shies or refuses to move forward, he has to move his hips around, side pass, back etc, hard ground work at a fast pace so he decides it's much easier, and more pleasant to do as he's asked and give the tarp a chance to eat him without a fuss.
I may lay him down simply because he still lacks respect. When the horse is laid down he learns that I can put him on the ground, first of all. When you lay him down it's important to sit with him and pat him and talk to him for a substantial length of time so he knows that he's safe. So not only are you showing him that you have control of him, and you can put him in the most vulnerable position possible for a prey animal, but you are showing him that it's okay for him to be helpless, he's safe. It's an extreme move, and I very rarely do it. In Sam's case, I believe he has so many layers of questionable training, it may help him have an 'absolute'.