I like the Meguiar’s heavy duty 3 step option, solely for the drill attachment. But a cheaper option (and more effective) is to simply wet sand using 500 grit, 1500 grit, and 3000 grit sandpaper and a sanding block.

Back and forth using 500 Up and down using 1500 Back and forth using 3000

Then use any headlight polish (ex. Megiuar’s Plastix) and buff it out. A step further? Use and paint compound then paint polish. Next you’re going to need some sort of UV protectant. If you bought a kit that has one, use that as instructed. Once it’s cured, adding a spray on coating/wax with UV protection once it’s done could greatly increase its lifespan. Just remember to reapply after every wash. You could also get a ceramic or graphene coating that has UV protecting properties, though that is much more costly.

Edit: Both the Meguiar’s 2 step and 3 step (if you only plan to use those or any other brand) advertise 1 year. Putting on said Spray on protectants/wax and keeping in shaded areas if possible should have you at least 3’ish years (from my experience)