How do you flush flush hydraulic brake system?

Answer 1

to start with if you are flushing because something other than DOT approved has been introduced to the system stop and change all components that have rubber in them ( for safety sake)

if not then all you have to do is bleed the system as per manufacture procedure as you add new fluid it will replace the old if you bleed enough through the system, if you have access to pressure bleeder and know how to use it this will go much faster