The master is the high point in the system, so I'd try some bleeding there next. My normal technique is to pop the resi cap off, make sure the resi is around half full, and have some paper towels handy, this can cause spurts/splashes. Give the lever four or five slow full squeezes and slow returns. Next, switch to a slow full squeeze but then let the lever go so it snaps back as fast as it can. When it snaps back watch the resi, you should have fluid flow in, possibly a fountain (splash warning!), and hopefully some air bubbles show up after two or three snaps. Alternate between slow returns and snaps, as the bubbles stop, slow pumps for a bit to get air collected at the top, snaps to coax it out. It can also help to 'twang' the brake line in a few spots to encourage stuck bubbles to travel up.
The other way to do this, use the banjo bolt on the master as a bleeder, resi cap back on, wrench on the bolt with paper towels to catch the spray around the banjo. A few slow full pumps to again get the bubbles collected at the high point, full squeeze, hold, and then crack the banjo bolt loose. You'll hopefully hear air then spurting, tighten it once the fart goes liquid. Repeat a few times and see if that gets more air out.
