I have a new to me tractor loader backhoe that is undergoing a fairly major R&R. The hydraulic system is full of chocolate brown milk shake instead of nice clean and clear hydraulic fluid. The manual for the backhoe (Ford 723) simply states to flush the hydraulic system, but what is the proper way to do that? What should I use to flush it with? What is the best type of filters to use once the system is flushed?