I just re-stripped a section of my boat last weekend. Sure, fiberglass is different than paint, but a few things I learned.
Heat is your friend, but it's not just heat to the vinyl, you actually want to get heat into the surface it is applied to. Taking vinyl off a black car that has been sitting in the sun all day is easy. Taking the same vinyl off a cold, white boat in the shade is hard. Use the heat gun, but don't get the vinyl so hot it melts. Try to work slow, working the heat into the surrounding surface for a bit. Don't try to apply the heat while you are pealing since it will melt the vinyl as you are pulling it off much easier than while it is stuck the car. Do not use Goof Off or other solvent until the last resort. Once you apply some goof off, it breaks down the vinyl into a gooey mess, and pulling it off will like trying to pull off a chewing gum instead of a solid piece of vinyl.
However, as a last resort, Goof Off did an excellent job of dissolving the left over adhesive, but I would keep this solvent off my paint as much as possible. Suppossed to be safe for use on fiberglass and paint. But don't let it dry! Keep a bucket of soapy water close by and keep the rest of the paint (that doesn't have vinyl) wet and soapy and any goof off that gets on it will be highly diluted. If you let goof off dry on your paint in it's concentrated form, it could cause a "haze" which will be a pain to buff out.
Do not use a razor blade to peel up the edge, just your fingernail. Paint a razors don't mix.
Good luck, heat is your friend, just not so much that you melt the vinyl.