This type of pistol's utility is based in its small size. But the things that make it useful to us also makes it hard to shoot well. There's very little to hold on to, so it's hard to land a consistent grip. Especially being presented from a pocket, cold, with minimal warning that you're going to have to play for blood. Slight variations in how you get hold of the pistol can make massive differences in where the muzzle ends up aimed without you having any real way of knowing outside some sort of useful sighting reference.
At conversational distance something like using the back of the slide centered in the head can certainly work...but it's also easy to have the muzzle elevated, depressed, or off to either side without being able to easily see that. This is one of the reasons why being able to work with an airsoft replica or a blue gun will be highly valuable, as you can figure out what you tend to do wrong and burn in some good practices. The shooting part of this isn't the most important part by any stretch, but it's still going to take some work to get it down pat.
This is one of those things where you are going to have to be very deliberate. It's tough to be deliberate when someone is sticking a gun in your face.