If your cutting around the anus , I like to use a long skinny blade like a filet knife so you push the knife in far enough to watch the blade as you cut around the anus. If you do it correctly everything will pull out together. I do this part after I remove the guts so I can see my blade tip while cutting around the anus.

Some people have trouble doing the anus cut without puncturing the bladder and find it easier to saw the pelvic bone. If you choose to saw the pelvic bone , just spread the legs apart , cut with your knife right down the middle (between the hams) until you hit the pelvic bone. Then use either an axe or pelvic saw (cabelas has them cheap) and make two cuts roughly 3" apart so you can remove that piece of pelvic bone and get at the entire poop chute.