My gelcoat a bit dull, and stains easily. Could not get out some stains with Spray Nine and Barkeepers Friend. Tried something called FSR Fiberglass Stain Remover by Davis. Worked great, and no, I don't sell it.
Jake: I agree. I use the blue gel FSR. I think 'On and Off' is a bit more powerful, but the ASR is less caustic and, especially when working on the hull bottom, less likely to splash or drip onto your skin.