In my business, I used a wax called "Carnauba Bay" It was relatively inexpensive but was tried and true. when i was waxing 5 vehicles a day...I didn't have time to play games with wax...A smeary wax job a 5pm would kill me. When I tried this stuff all I could say was i couldn't believe how well it works. EVERYTIME!!
I can't tell you how many black vehicles I waxed(after buffing) in the direct sun.
The first black vehicle I did with it was a Mercedes 500 coupe and the phone rang. I came back to find the wax "baked on" from the sun coming through my shop window...I grabbed a towel and started taking it right off...Worked excellent I still use it to this day...Never a problem!
Here's a link I found to get some...I have no affilliation with them. But there's a fresh tub in my detailing bucket right now...
http://www.chem-quest.com/carnauba.htm