Does movement help? Passive range of motion exercises can be quite important to prevent pain. When he was pretty much completly paralyzed my PALS had physiotherapy four times a week. This was a great luxury (and it would have been even better to have those sessions each day) and one of the thing that really improved his quality of life.
The other thing that comes to mind is positioning. Each limb should be supported to distribute the weight evenly to protect the skin and everything.
An ergotherapist once very skillfully positioned my PALS on the side, using all the pillows he could find and various towls that he rolled up and placed in nooks and grannys. About the quarter our after he left my PALS asked to be positioned on his back again. This was like an unboxing video, haha, so much packing chips!
After that we ordered a dozen positioning pillows in 3 different sizes. They are filled with little "styrofoam" pearls and are very easy to use and push into the shape you need.