Homebrew PCBs

When milling a circuit board on a CNC, I can see two possible 
approaches...

1) Using a 'V' shaped bit to outline the traces. This leaves a lot 
of the copper on the board.

2) Using a flat bottom milling cutter and cut away all of the unused 
copper.  

As I have never done this before, is one method preferrred over the 
other, or perhaps even another way of doing it?


Chris

Also, what happended to all the discussion on building a CNC machine 
for this purpose?  There was a bunch of talk, then it all seemed to 
dissappear - did it get moved to a different group?