Answer
For fiberglass shower scratches, wet sand with 800 or 1000, then 1500, 2000, and 3000 before polishing.
Why it happens
Fiberglass gelcoat or surface finish needs fine wet sanding before polishing.
Recommended grit
Use 800 or 1000 for light scratches, then 1500, 2000, and 3000.
Wet or dry
Wet.
Success check
The area has an even fine haze and no deep visible sanding lines.
What to do
- Clean the shower surface.
- Wet sand the scratched area with 800 or 1000.
- Refine with 1500, 2000, and 3000.
- Polish after the scratch pattern is even.
Avoid: Do not use coarse grit on a finished fiberglass shower surface.