Island Girl
While expensive, I can recommend the Island Girl system for fiberglass restoration. http://www.islandgirlproducts.com/ The site looks low-budget, but the products really work. I used them to completely restore my faded, oxadizing hull. And yess it works wonderfully for removing chalkyness from dark gelcoat colors like black, blue, or red. Actually it also removes chalkyness from white or lite gelcoat, but the result is the most dramatic with dark colors. The minimum products you would need are SeaGlow, SilkenSeal, and SB Superwax. There are great videos and typed step-by-step instructions on their website. If your hull has a lot of oxidation, you will need more SeaGlow. Maybe three 16 oz bottles to do the whole hull. And believe me, once you do part of your hull, you'll want to do the rest. This stuff even removes deep set-in stains, like that yellowing that builds up around the waterline. Check out a pic of my boat as I was partway through using SeaGlow here: http://www.mnagy.net/mac21/index.php?categoryid=4&p17_sectionid=4&p17_imageid=15 Disclaimer: I am in no way affiliated with Island Girl, I just think that their products really work since they did for me.