dbrufus,
Sounds like you have a combination of things going on honestly.
First, an hour of cooling time is no where near enough time for a black car in 90 degree sun. 3 to 4 hours is a smarter move. Iknow that's hard to do, but black is a mean mutha to maintain.
Second, likely a bit too much product was applied. However you may have contaminants on the paint that are holding the product and making it appear that your using too much, when in fact your not.
All that being said, when was the last time the car was claybar'd? If you don't know, or you have never done it, I'll bet you have some contamination on the surface that is grabbing your wax.
Best thing you can do is clay bar a small area, then wax like normal. Willing to be all will be good.
Also, Another way to tell if you have contamination, is with your spray detailer. If your spray detailer takes more than one or two wipes with a microfiber towel to remove, then there is contamination on the surface and it's claybar time.
Black tells everything, very high maintenance.