IMO the CZ 82 is not designed for single handed mag release. The ergonomics and grip design are just not there for me anyway. Being right handed, I hold a firm grip with the thumb and forefinger resting on the grip panels. I bring my left hand up cupped as support. My left thumb is under my right thumb and pointing at the target. The fingers of my left hand wrap around the lower three fingers of my right hand.
To change mags, I keep the pistol on target and release mag with my left thumb as I'm reaching for the next mag. After inserting mag, my left hand goes back to the support position. With a bit of practice I am able to do this rather quickly while keeping the weapon on target.
I can operate the mag release on my CZ-P01 with one hand. I prefer to use the above method, since I carry my CZ82 most of the time and that's how I trained...
I was taught to: focus on the target as you draw your weapon. Once you weapon is pointed at your target look at your sights. They should be right on or pretty close. If not, you may not be holding the weapon correctly or the weapon is not suited for your hand...