You can't put out a request for points on the rental board here. You just have to go through the threads of people offering their points and reply to them.
David's is more expensive, but also more secure. I used him before I knew more about DVC and recommend him to others because he does the leg work of verifying and then will refund your money if you get there and there is no valid reservation.
But for the savings now that I know more I would rent through the boards. It is more time consuming, but if someone has the points you need it can work great.