This is what they use in dump trucks to help materials slide out. http://www.quadrantplastics.com/na-...tandard-175-f/quicksilver-R-truck-liners.html It is tough you could load your tractor on it. Not sure how much it would help with manure. I have a hard enough time with dirt sticking in my dump truck.
You could also try a cougar vibrator. These are used in a lot of dump trucks as well to help move sticky materials.Cougar(R) DC Truck Vibrator
Neither of the above are cheap. Cheapest solution would be line the bottom with wood shavings or hay as others mentioned.
You could also try a cougar vibrator. These are used in a lot of dump trucks as well to help move sticky materials.Cougar(R) DC Truck Vibrator
Neither of the above are cheap. Cheapest solution would be line the bottom with wood shavings or hay as others mentioned.