You'll get a lot of different opinions on here as everyone has their own preferences,
but as Ekona said, Poorboys Black Hole is great stuff for covering up swirl marks on dark coloured paint.
To finish off, I use Sonax Brilliant Shine Detailer. Easy to apply and water just beads off for ages & ages afterwards. Awesome stuff!!
I'm just about to try Sonax Profiline Polymer Netshield, a sealant, which is like BSD, but with muscles!
Each application is supposed to last up to 6 months.