If you don't wanna keep buying kits, just get some 1500-2000 grit sandpaper, wet sand it real good, then use a bit of metal bright metal Polish and buff it real good, as long as the inside isn't foggy
Are you headlights condensated(from the inside) or hazed(from the outside). They're two totally different things that require different things to be done.
Condensation will require you to re-seal your headlights.
Hazed lenses require you to wetsand/polish/wax & seal them.