Polishing is the step where you actually remove the swirls, oxidation and ultra fine scratches for good and restore that like new shine again! Polishing is generally regarded as the most important step in the detailing process because it creates an optically clear surface so you get that deep shine back where as the sealant and wax can only enhance the way the paint already looks.
We generally recommend a two step process with a light and medium polish and pad combo for best results. However if you only have light imperfections, we would recommend a one step polish. The Menzerna SF 4000 with a white or black pad is a great polish combo that will remove these light imperfections while finishing down extremely well.
These polishing steps generally work best with a buffer. We have a completely safe and highly effective option if desired in the Porter Cable 7424 XP. If you don't want to use a buffer we generally recommend a one step process with the Meguiar's Ultra Finishing Polish M205.
We also have various other resources to help you learn more about polishing. Check out the polishing sections of our Detailing Guide and Ask-A-Pro Blog.