Brake warning light on dash

Well after throwing away the NEW 7/8 bore wilwood master cylinder that would never bleed all the air out I put a stock standard drum/disc master cylinder on and I have a solid pedal and light is off. Now my question is, it appears there is residual pressure on the rear calipers. I am assuming from what I have heard the residual valve must be removed when doing 4 wheel discs. Which port is it on? The port that goes to the rear wheels with small reservoir and farther from firewall? After bleeding I cracked the rear bleeder and a small amount of fluid did come out without pedal applied. Ive seen after a google search to put a screw in the port a pull it out. correct? Thanks