[ls1ac]

Sounds like if the first push is to the floor and then the second is good then the pistons are coming off the rotors too far. Check to see if the rotor is warped or wobbling and pushing the pistons back. Air in the system will give a soft push no matter what. If fluid is leaking out it would take a lot to make a full pedal travel.
I have seen a bad master cylinder that required two pumps to get pressure to the system. The seal was bad because the rubber was old and hard, second push it would open up and seal.