yeah, depends on how much of a mirror finish you want. I did both my AC64 and my TRUE as well as my 3600+ and 5000+ cpus, more for the **** of it than anything else. I did the TRUE up to 2000 grit and got a mirror finish (not perfect mirror) and the rest up to 1000, to be honest I cant see there being much of a gain after 600 grit. I used a flat piece of 3/4 steel sheet I had lying around but as mentioned above a pane of glass is fine too.
You can get the paper from pretty much any autobody store, even some hardware stores will have well into the 1000 grits.