For the Finger Roll achievement, you can go for a lay up like you would a dunk, but while you're in the air, just press
For Clean Sheet, if someone doesn't have extra controllers, playing a game of 21 will be easy to shut them out. Just make sure you score the first points, and then you will start with the ball every time. I used LeBron James on the Miami Heat, made the first basket, and then I just shot a 3 pointer right away and it went in every time, especially once you're on fire.
edit: Clean Sheet method actually doesn't work.