Don't drain all the fluid out of the system first, that can be a major problem later trying to get your ABS back up and running. Just put fresh brake fluid into the master cylinder first, then unhook one line at a time, reinstall the new line and open the bleed valve allowing it to drip until the brake fluid comes out clear, then go to the next wheel. Start on the right rear and work your way forward. As long as you let each caliper gravity bleed untill you get clean fluid you won't need to pump/bleed the brakes when your done.
Mike J.