I didn't flush out the core, but I drained most of it out from one of the plugs at the bottom. It only used up about one gallon, and now I have a 50/50 mix left over that's also a gallon.
Just thought I'd give a heads up for anyone who was curious.
Also, changed the brake fluid from factory crap to ATE superblue. Stops on a dime now. MUCH better feel.