Disconnect Master from Push Rod
There is a rubber o-ring on the end of the pushrod that fits into a groove in the master cylinder to keep it from inadvertantly coming out.
When they are old dried out and hard it can be quite a chore to get the push rod out.
I have never had to resort to cutting apart a MC to get them to seperate though. I always squirt some lube down in there when they are stubborn and that has always worked.
I use some grease on the ring when I put a new one on in hopes of not having a problem when I take it apart the next time.