Install from DVD set

[Richard Owlett <rowlett@cloud85.net>]

I've a machine on which I've installed Debian Squeeze from 
the 8 DVD set. During installation I did not chose the 
option to scan DVD's 2-8.

Questions:
1. After an install completed, how do I scan the other 7 
DVD's so Synaptic knows about all available packages?
2. I know I've seen the answer _somewhere_. How could I've 
found the answer myself {using search function of debian.org 
and wiki.debian.org was unproductive)?
3. As I'm doing a number of test installs to the same 
machine, I'm using preseeding. How do I force the installer 
to ask if additional CD's are to be scanned? Manual input 
during a preseeded install is obviously possible as the 
installer will fall back to manual if there is missing 
required input.

TIA