Undercut someone by 1 gold, 15 silver, and 39 copper with one item. When the item is purchased repost two at the same price. Keep doing this until you get undercut.
Do you have to use 1 gold, 15 silver, 39 copper? No, but the purpose of this experiment is to show you that a random undercut (by random I mean it looks like a robot decided the number), does not come across as an aggressive takeover or undercutting war. The seller above you will either buy you out or just wait until your item has been sold. I'd say undercut by 5% with some random silver and copper ammounts mixed in.
Try to do this at a time when you can check the auction house about every hour for about three hours. Each time you check simply increase the number of reposts by one if any of your items have sold.