This series of pictures shows the little-finger figure-4 brace in various positions, using both your left hand and your right hand. [I personally prefer my right.] It probably works best with right to right hand and left to left hand. What is important is that your digit closest to your opponent’s hand presses down as your second digit serves as a base. It almost works like a jutte. As long as you can maintain the pressure you can move the opponent’s hand [and thus his body] as you wish up or down. You will need to “play” with this technique to get the right feel so as to be able to maintain adequate pressure on the attacker’s little finger [a figure-4 lock] to control the attacker’s upward and downward movement.
The complete technique can be found on pp. 171-175 of Jujitsu Figure-4 Locks.