No idea how they do it because I aviod them as much as possible, plus I cannot watch them. Go to the autoparts store and but a flushing tee-kit along with a new heater hose (that you will cut to place the tee in) and buy some DI water at the grocery store. You flush it yourself with a garden hose and the engine running.
94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new
88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new