Once buffed, always buffed ? please help

geddy lee

I have never had a car professionally buffed until recently. I have always taken care of my cars , 94 Alpine Silver Supra, 03 Silverstone 350Z, using products from Zaino, Meguiars, etc. I bought a 2009 370Z in Magnetic Black back in May. They told me it had been professionally waxed and buffed just before I picked it up so I am assumimng they used a porter cable or something similar. The car looked great on delivery. I was going to wax it this week so I tried a small amount of liquid Meguiars Ultra on a small spot. When I wiped it off I could see a definite difference between the buffed paint and the spot I just did which looked duller than the rest of the car. Am I doing something I shouldn't do? Does the car have to be buffed from now on. The black is tricky anyway and I don't want to f**k the paint up. Does the porter cable really bring out that much more shine than hand waxing? Thanks for your help.