Debugging Core Data / Interface Builder


I tried this chapter this afternoon, but ran into problems getting the app working,

Two questions:
[li]What is the best way to spit IB sessions into chunks?[/li]
[li]Is there a way to debug mistakes made during IB sessions when using Core Data?[/li][/ol]
On point 1. I did try using smaller chunks of work, but obviously something serious was missing, as I ended up with the app running away (symptoms - mouse not responding, huge swap file. I had to kill the task).