Mathew,
It is a catch 22, if you bring the switch to neutral you cannot talk to each other, leaving on INT mechanics can hear everything. So normally I leave the switch in INT position and whenever I want to speak to FO and want it sensored I bring the switch to neutral and direclty speak to other pilot without any of the electronics.
CJ,
During pushback I keep the switch in INT position and talk to engineer directly without pressing any switch. Alternatively, I have some people keep the INT switch in neutral position, select the intercom TX and use RAD to PTT. I find the later one more cumbersome so during pushback I keep it on INT at all times.