I asked a professional football coach this question a little while back as I've had the same thought. In terms of skills to emphasize, he said that reinforcing the idea of creating passing options on the pitch for the man in possession is crucial. Ball control and being able to look up and make a pass sharply is important too. But the main thing he said was the players have to have bravery on the ball, and I feel that such bravery comes from confidence in themselves and their teammates. If it is something they practice every week in training, that they know the people their passing to and know that they know what to do too, even as well that they know what to do if they lose the ball too, then your boys will start doing it more often. Encourage teambuilding and problem solving tasks that confine them to build-up play in defence, and over time they will have the bravery in them to execute it. 

I asked a professional football coach this question a little while back as I've had the same thought. In terms of skills to emphasize, he said that reinforcing the idea of creating passing options on the pitch for the man in possession is crucial. Ball control and being able to look up and make a pass sharply is important too. But the main thing he said was the players have to have bravery on the ball, and I feel that such bravery comes from confidence in themselves and their teammates. If it is something they practice every week in training, that they know the people their passing to and know that they know what to do too, even as well that they know what to do if they lose the ball too, then your boys will start doing it more often. Encourage teambuilding and problem solving tasks that confine them to build-up play in defence, and over time they will have the bravery in them to execute it.