I read quite a lot of stuff on detailingworld last year before trying my hand (for the first time) at amateur detailing.
As posted above, don't mess with a big rotary polisher until you really know what you're doing - it's very easy to do more damage than good. It's harder to do damage with a DA polisher than a rotary!
Saw a suggestion - go to local scrappy, buy a cheap bonnet with poor paintwork, use it for practice before you use a machine on your P&J. Seems like a good idea!
I was lucky enough to get my bonnet professionally mopped at our club cleaning day a while back - and he used 3M stuff mentioned above, 3000 grit equivalent which is very fine! However, it's damned expensive and theoretically only availoable to the trade - you can buy it online from 3M but you have to tick the box that you're a professional! I used Bilt Hamber normal clay first, then I've got a small 12V twin pad polisher fitted with proper Sonus pads, it's very low power so stalls if I get heavy handed. AG Bodyshop 03B (1200 grit)and 02B (2000 grit) with a water spray got rid of a lot of the swirl marks I'd put into the paintwork with a standard cellulose car wash sponge - but ot took a while!