What Shark said, except in true definition, you can't do a push shot.
But I know what he meant.
Sometimes, people have a different view of what constitutes a Push Shot and a Double hit.
I have heard players mix up the 2 definitions.
2 Frozen Balls. Yes, you can push thru it, but still have to do it proper, in order not to perform a true Push Shot and Foul.
If you can find it. Referee Quiz on Dr. Dave's site. Bob Jewett takes you thru a ton of different shots.
The Frozen Ball shot and how to do it proper is shown several different times.
The Not So Frozen Ball shots, Tangent Lines etc, are also shown, how to do them and avoid Fouls.
Even if you are not a Ref, I highly recommend watching the videos. You will know what is legal and what is not. The most important part, how to do it yourself and also recognize another player Fouling those shots.