Spongy brakes?

I have replaced master cylinder, bench bled twice, brake hoses on the front, new brake pads, new booster, bled the system numerous times, and there are no leaks. Yet the brake pedal still goes to the floor. Pumping the brakes will build up some pressure but will go down. I see several articles regarding adjustment of the pushrod in the booster and that there is a special tool(or by trial and error). What is this tool and where do you get it? Are there other things I should consider before spending time removing the master cylinder over and over. From what has been posted, its a crap shoot.