What I've learned about ballasting so far:
- It's always easier to add more ballast than it is to taking it away
- Working around switches is not as hard as it seems, you just need a lot of light and a careful hand
- Dentistry tools are very helpful!
- Don't let the ballast creep up on the inside of the rails. If you test the track surface with a boxcar and it seems smooth, beware that a locomotive with deeper flanges will bump and scrape over the same section
- Overall it seems better to ballast first then do the groundcover around it, since the width and slope of the ballast edges is more a matter of setting it up by eye than measurement
- It's tedious but the layout looks so much better once it's done!