start using that right stick left and right for jukes and other moves for RBs with high stats in the Elusive category. they are more effective when you are not using turbo and sometimes it helps to let go of the left stick. practice this stuff in practice mode, without defense and then with a defense.
stiff arm is the X for PS3, A for xbox. obviously the strong RBs will use the stiff arm more often and effectively.
with both of these moves you want to use them right before the defender goes for the tackle.