Sanding Bondo Spot Putty

Hey guys, I was wondering what Grit should I use to sand down Bondo's Spot putty? I have heard finer grits, Can anyone explain what a " finer " grit is & where can I buy it? Also, does it matter what kind of sand paper you use to strip paint? or sand the Spot putty?

I've hear 320-400 grit paper works, where can I find this paper?

Strip the spot putty. Spot putty is a pile of shit. Use Bondo Body Filler, or Evercoat Eurosoft (same thing but 3 times as expensive).

When people say finer, they mean a higher grit. For shaping body filler use 120. Then go to 320, then 600 wet sand. Then 2000. And after everything is fine, sandable primer. Any auto supply store, Home Depot, Lowes, Wal-Mart has it.