Front brakes are always harder to bleed effectively because the master is so much farther above the caliper and allows the air bubbles to become trapped easily.
Try Dinqua's sure fire method, once you get a little back pressure from the front pads button it all back up and tie the front brake lever at full lock with a bungee overnight. This will force the bubbles back up the line and the next morning you can finish off with just a couple of pumps.
