Restoring gelcoat shine is a labor intensive endevor. That said well worth the effort. I did mine last season the material alone cost around 500.00. That did not include the bottom of the hull. I started with 800 wet sand paper keep wet then went to 1000 up to 2500 I then used marine formula 3m imperial compound then went to aqua fina polish finished it off with marine grade wax. All products used were 3m my personal favorite for over 30 years. Jamestown Distributors is where I ordered mine they have videos of the compounding process.
Who ever said nothing in life is impossible.
Never tried slamming a revolving door.