| Air bubbles tend to move up. It is possible that in normal bleeding that you are trying to move bubbles down while between each stroke the bubbles are moving back up. Reverse pressure bleeding has been successfully used in systems where nothing else seems to work. Both the bubbles and the new fluid are forced up into the master cylinder from the slave cylinder in one smooth action with no pumping required. I plan on trying this out next time I bleed my clutch using my Mityvac vacuum pump which will work in reverse by using the exhaust port on the pump to pressurize the Mityvac container partially filled with brake fluid. 
Mityvac brake bleeding kit (About $30)
First step would be to do a normal bleed to clear the slave cylinder and lines of old fluid and debris. You don't want to be forcing contaminated fluid back up into the master cylinder. Next step would be to make sure the master cylinder is empty.
Add fluid to the container 3/4 full (3 ounces) leaving air space to be pressurized. Hook it up to the bleeder at the slave cylinder. Take a couple of strokes on the pump to pressurize the container. Open the bleeder to release about one or two ounces of fluid then close the bleeder. Release sufficient fluid to fill the reservoir to the proper level. Assure bleeder is closed. Release pressure on the container and disconnect. It might also be wise to repeat the procedure at the bleeder on the right fender.
For anyone interested in this concept, Mityvac describes the procedure for reverse fluid bleeding which uses their more expensive Hydraulic Injection System Shooter.
[ http://www.mityvac.com/hydraulicclutchlinkages.html ] The RSI power bleeder is used for reverse bleeding on motorcycles. This should be available at most motorcycle shops. Their much simpler procedure is described here:
[ http://www.maineiactrials.com/RSI%20Power%20Bleeder.htm ] Although I haven't tried it, it seems to me that this might be the way to go.
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Reverse pressure bleeding might be best of any procedure. - 
