Re: black paint
For black paint, considering your paint is in good condition but with 2years of ageing on it, i suggest the the 3 stage ultimate wax system (ceaner, glaze, pure carnauba wax) especially if your paint has a couple of scratches or sirl marks. Carnauba will make your black paint much deeper and slick, which yoou may like more than using Synthetic based wax. You can also go the reflections route (car wax, then top coat), its a synth/carnauba hybrid, so it should be easier to use, something you might want since the yukon denali is quite big.. If your paint isn't in too bad condition and want to use a good easy to use wax, FX synwax is a good choice. Reflections car wax and FX synwax have MILD cleaners in them, so you have the option of using Step 3 carnauba wax or reflections top coat to finish of your paint.
Before anything else, you should use a quality car wash, then clay bar your vehicle. You'll be surprised how much easier the car wax (or polish/cleaner/glaze) goes on and off, and how much slicker the surface is after waxing.. I guarantee it!