Headlamp refurb question

[david75]

I need to refurb my headlamps. See pic

I’ve done it before successfully on another car so I know what to do with the kit with the different grades of abrasive paper, compound and polishing attachment for drill.

But people say it’s best if you then apply a top coat to protect from further uv degradation.

What top coat have folks used, how easy to apply, and with what medium/long term results?

Thanks