I would put a light sheet on so his body stays clean when he roll and keep putting the slinky on since you say that works for his neck. Also, could you wash just his legs in the morning or keep him in a stall the night before the show? Or maybe you can put some boots on him that have buckles to keep them on. They might not cover all of his leg but it might help some.
That's all I can think of right now but good luck at your show and be sure to get pics!