Several appearance questions.

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1. I have black spots that appear on-in the gel coat. Some wash away and to remove others, I have to us a Mr. Clean magic sponge.
2. When looking down the hull. I have shiny then dull, then shiny then dull patches. It's like I wax a 2' wide portion, skip 2', wax 2" skip 2'. This occurs on both sides of the hull.
3. Cabin fiberglass has no shine at all.
4. How do I repair/recoat the rusted fender trailers?
5, Gel coat cracks and dings. Most folks here I have talked to about repairing my gel coat cracks and dings must be on drugs. I could buy a newer boat for what they ant to charge. Is there a web site for DIYers? I need a lot of guidance and photos. I made one repair w/ 2 part epoxy, but it was where one of the screws the hold the Bimini top pulled out.