Hi Karen,
I should go look since I just purchased some yesterday, but I've always had good luck with a boat fiberglass color brightener and then boat polish that you can get at the Fleet Farm stores. I think Star brite is the brand name and they have quite a few different boat cleaning products. I'll try to check and update this a little later. (Just checked and what I purchased yesterday to get ready for next week's event was Star Brite Sea Safe boat wash, Star brite fiberglass color restorer with PTEF, and Star brite presoftened boat wax)
I don't remember if there are "Fleet Farm" or "Farm & Fleet" stores in the Minneapolis area, but those two chains carry much of the same merchandise. There's probably other similar stores that carry those types of products also.
If any others have had problems with these products or know of some better, please jump in, but so far I've had pretty good luck with what I get from Fleet. I used to use rubbing compound for the difficult stuff, but you have to be real careful not to overdue it on the Gelcoat.
I probably should have done this before even commenting, but one super nice thing about this forum and the ClassicGlastron forums that I love is that if you do a search on something like this, the topic has likely come up before with all kinds of helpful advice! And as you've seen, there are many generous (and far more knowledgeable) people who will try to help in any way they can!