Well Mel hit some of the points that I wanted to make. A couple of things I would add is that unless you train alot never try and get control of the gun unless you can touch it. I have seen to many times where people have been killed because they made a move to gain control of a gun and the attacker side stepped and shot them. They just did not understand the body mechanics involved to know how to close the distance. There are ways of closing the distance so that it is hard for the attacker to repoint the gun at you by the time you gain control of the weapon hand but you have to know how to step.
In the style that I train in, we try and move so that our body is between the gun hand and the free hand(inside)this is not always possible. This makes it harder for the attacker to switch the weapon between hands as you are trying to do a technique on one hand.
Be careful in using kote-gashi because if you do not put it on properly at the start the attacker is able to pull the trigger. As Mel said you have to be worried about the people around you. You should be out of the path as you are doing technique put who is placed into the path as you move the gun?
My instructor Robert MacEwen puts out several tapes and one of them is on handgun disarming. The tape shows methods of taking the gun by working against the attackers weak points in the hand. By doing the methods shown there is less chance of turning the weapon towards someone. He also has done training of FBI instructors on hand gun disarming. We also do alot of work with police officers locally.
I have trained with people who have stress 2 points: Keep it simple, find one technique you can do from a variey of angles so that you train your body how to move without any thought of which technique to do. The other point is to move the hand with the weapon down and away from the baody so that if it goes off you are not blinded and there are less flash burns. These are also good points to play with.