Dribble bars can be used to keep the concrete surface wet so the manure does not stick.
Have been used on round yards draining to middle to wet whole yard but generally are only useful for small areas. They can use more water than they save.
Tips on Getting the Best Result
Use before cows enter yard for milking and turn off when cows arrive.
Pros and Cons
Home made, effective if enough water is delivered, no labour required.
Concrete may become slippery if not allowed to dry out, difficult to get good coverage, may upset cow flow if placed at dairy entry.
Issues in Making it Happen
No labour required