I understand that the main quest can be completed without taking sides in the civil war, but I'm at the point where I'm contemplating finishing the main story line. I'd like to go back and do the civil war afterwards. Has anyone done that successfully?
I've done this succesfully. The main questline was one of the first questlines that I finished (mainly to get the Dragon Shouts exclusive to it), and the Civil War questline (the Imperial Legion path) was one of the last questlines I finished (because I can't decide who to support, initially).
If you do not trigger these bugs, or have done a workaround, you should be able to complete the Civil War questline even after the main questline has been finished.
The thing is, you have to do part of the main quest lines in order to do the civil war quest line, because the Yarl of Whiterun won't pledge allegiance with the Imperials until you go into Bleak Falls Barrow and retrieve the dragon stone for his court wizard. I imagine if you do the civil war quest line before you finish the main quest line, the peace meeting the gray beards put on might not happen (haven't tried it) because in the civil war quest you
kill Ulfric (as an imperial soldier) or kill General Tullius (as a storm cloak), both of which are at the peace meeting.