The best way to do this is by using the RB (juggle) and the left stick to hit the ball over your opponent. Here is how you set it up, this can be done with any team and any skill level.
Isolate your player with a defender 1 on 1 and make sure you have enough room behind him to get the ball after you hit it over his head.
Next, start juggling by holding RB. Once your ready, just use the left stick and push it forward and your character will hit the ball up, pass him, and catch it on the other side.
Retreat back to your original position with the ball, rinse and repeat until it unlocks. You do not need to score a goal, or end the match for it to unlock. Hope this helps.
Edit: If you play Freestyle mode, and just tap RB (continue juggling), wait a few seconds, or keep going until a defender gets too close, and use the left stick to go forward, you get points for completing each juggle. I got 800-1000 per try. So this might be easier.