No! That's definitely one thing our Docs have not asked us to do (yet)!!
AND, I would have serious reservations about doing it if I WAS asked. No Way, Jose! Too much opportunity for a perforated colon, if you ask me! I'll stick to doing my job, and let the Docs do theirs'. If they're unable to manipulate the controls and push at the same time, it would be my suggestion they are in need of some serious competency recertification of their own.
Sorry if I sound so incredulous about this, but it blows my mind to think a GI Doc would even ask me to "push". Let's face it, there lies a major portion of the risk for perf. Would the driver of a car be likely to ask you to push the gas pedal for him? MeThinks not!
Guess you have to check your own facility's Policy and Procedure Manual and your State Nursing ByLaws/Guidelines, and then do what you feel comfortable with.