the easiest way to pick locks is to move left stick slight to the left and try if it breaks when it resets move slighty to the right and try. Basicly try to figure out which side the release is on then try to narrow it down by making small adjustments everytime the pick starts to rattle.
Slowly and carefully attempt to open the lock. If the lockpick is resisting, you need to move it until it stops. Be VERY carefull with turning that lock, because i've had the pick break when it was nearly open.
Also, it seems the harder chests are easier to open. They give you less room for error, but that means that you won't get the pick jamming as ur in the middle of turning the lock.