Any advice for wet sanding and polishing??

[scherp69]

Hopefully on Monday I will get a chance to start wet sanding and then polishing the firewall. I'm probably going to get the Makita 7" variable speed buffer. I have wet/dry paper starting with 800 grit going up to 2500 grit. Does anyone have any advice/tips for doing this. I've never done either before so any advice would be greatly appreciated. Thanks in advance.

Here's a pic of the firewall I'll be doing.