Plugs for lines
Sorry, I addressed another query not on target w/the original post, now for the OP. If you have the batt. diconnected, or don't mind pulling the stop lamp fuse, simply use something to hold the brake pedal depressed. This blocks the ports and prevents fluid from gravity flowing your master dry, do it all the time at work for decades now, was tired of wearing/
standing in brake fluid changing/fabbing rotted lines. That is all.