Since Bill and I sell automotive and body shop supplies, this isn't new to us, but it might be helpful to some of the DIY people out there in cyberland. Rather than go into detail, here's the link to a forum that has great pictures and directions.
*Note - you don't have to use the brands of products that he uses, just something comparable. If you don't have the fine wet/dry sandpaper, you might try asking a local auto body repair shop if they'll sell you a sheet of each. Just tell them that you're working on a project (just don't tell them it's this project).