I recently did this. Remove the entire reservoir and replace the hose that goes from the Res to pump as it will fail, if it hasn't already. It goes rock hard and splits. You can use rubber hose from local autozone etc if time is an issue.

Take the reservoir out and blast it with brake cleaner.

Once its all back in, I recommend you flush the system clean. Run the return line into a container and start the car and just keep pouring in flesh fluid until it comes out clean the other end.

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k