All great advice. As a professional instructor I find that most often the worst teacher is oneself unless you're able to rope in your excitement and truly practice correct technique.
The key to learning accuracy, like anything else, is starting slow. Paintball is just another sport in which you use muscles one way or another to accomplish a goal. In this case, its shoot someone in the face!
You've heard the term "muscle memory" before, I'm sure. Just like driving a car, you don't think about what you're physically doing so much as you think about what you have to make the car do. Your leg knows the muscles that need to move, and how to move them to produce braking with the car. Driving stick is another great example. Having a fast and accurate paintball shot is no different.
In order to build muscle memory you must first develop good technique. NEVER attempt to be fast when learning technique. Speed comes naturally. You cannot gain speed (properly) without first having skill. Think about reloading. At one point you had to concentrate on reaching into your pack, releasing the strap, pulling the pod out, realizing you should probably open your lid on the hopper first, opening the pod, and pouring paint into the loader. You probably go through that motion much more smoothly and faster now.
So anyway...first get a comfortable grip on the gun that allows you to keep it stable and sight down the barrel precisely. Practice slowly coming out of a bunker, aiming at a target, and shooting until you hit it. Do this repeatedly, AS SLOW AS YOU NEED TO so that you're hitting the target before you come back into your bunker. There's no point in practicing ****ty technique quickly. Do it slow first. Increase the speed gradually and naturally. If at any point you catch yourself making an effort to go faster, you're going to fast!
The speed WILL come. It's more important that you hit your target with precise technique than simply shooting at your target quickly.
Practice properly over and over again and you'll see results. Best of luck