The veggie oil is a good way to help.. Also you can fill your tub with about an inch of warm water, place your beardie in it. Once your beardie relaxes this will help him have a bowel movement as well. The video is short but it shows how my beardie relaxed at the end.
http://www.youtube.com/watch?v=brx5iZxaU_c I only let him sit in it for about 10 minutes, beardies can get respiratory diseases so limit how much time you leave your beardie in the tub. I would suggest once you give your beardie the oil, only a little bit, you wait atleast an hour. Give time for the oil to digest and work its way through the poor little guy. If the beardie does not have a bowel movement in the tub, wait a day and try again.. Inspect your beardies belly, if you feel a knot then he is impacted. If that is the case limit feeding. You dont want it to get worse. Once your beardie has pooped, try feeding him more greens and veggies, dont use sand substrate in the bottom of the cage (when he feeds he can ingest the sand and cause more impactions). Sorry I was rambling... Good luck