Talk to me about staging

[nomad]

This will be my first layout with staging ( maybe ). My garage layout will be point to point with staging at both ends. The staging yards will be stub ended with run around crossovers. Now, I make my first staging run, switch some industries and an interchange along the way, go to staging and run around the train. To me, that train will now be "unworkable" going back. Am I correct on this, does the whole train need to be turned? Or am I overlooking the obvious? Also, would there be a train at each staging yard, or would one run back and forth between the two? I think what I am really asking is how do you use staging?
Any info would be a big help.

Loren