Last time I did this the recommended way (flush thru the system starting furthest wheel from MC) that brake began leaking a week later. All the heavy crud went into the slave cylinder and settled there (drum brake) damaging the rubber. I was young and this was the first time I did this procedure.I was PO-ed since there I was trying to prevent exactly what I just caused! I guess best practice would be to rebuild the cylinders after a flush or ?