ABS brakes
 

I just changed out my rotors and pads, now the pedal is soft and spongy feeling. I was told that by pushing in the calipers you bleed brake fluid back into the ABS system and this will cause some air entrapment. The brake system was never opened and bleed. A couple of people said to do some heavy braking at high speeds. They said this should cause the ABS system to come on and the some how the system should bleed itself of the air pocket by forcing fluid back and forth into the system. Is this true? Any suggestions?

2002 ML500
All 4 rotors replaced and new pads with MB parts

Kind off OT, but what made you want to change three year old rotors?