Well, what I do is option-double click on the pre-comp in the timeline, this opens it up so you can work in it. If you have “Syncronize Time of All Related Items” checked in the General section of the Preferences, this will make it easier to see what you’ve done in the original. Also, if you have enough monitor real estate, you can separate the windows and timelines for the pre and the main to help see the end result.
FWIW,
Jeff O’Brien
Windward Visual
Lake Oswego, OR