I started out using a knife as some have stated, then went to a small hatchet, but it left too many sharpe pieces to cut the wrong things and my hands. I then started using bull nose loppers. Smooth even effortless cuts of the pelvis. Also while field dressing you may want to elevate the rear portion slightly above the head so all the mess doesn't flow over the hams. Let it flow out the front. Good luck.
Jim