At the BJJ/Kickboxing place I went to they did a technique where you do a takedown on the attacker and then doing a knee drop type of move.

Basicly you would fall into a one legged kneel in order to hit the person with your first knee and then turn at the hips and bring the first leg up and the other leg down into another kneeling position to hit them with the second knee. (I realize that's not a very good description, I'm working on trying to find a video on youtube or something) It was a movement a little like the knee walking done in Aikido.

Does anyone have any experience with this move that can give me more information about it or know any other methods of using the knee against a downed opponent?