Jasol, welcome to the Optimum Forum! I'm guessing you're right about the heat - high heat causes Coatings to flash and cure much faster. There are several possible solutions - an easy one is to add another layer of Gloss-Coat to even high spots. Another is to try a cleaner wax lightly by hand to see if you can reduce them. Since you can layer Gloss-Coat, it shouldn't be necessary to polish an entire panel.
EVERYTHING is more visible on black! As you've found, light is not an absolute solution - things become visible in various lighting scenarios - sometimes twilight shows imperfections better than a spotlight. The best recommendation I can make is to do very small sections until you get a sense of how fast the Coat is flashing - you will save time in the long run