So the chicken (rooster actually) got done and now it's time to report back on what went wrong, and what went right.
The bad
1. I did cook this bird without gutting it. The intestines did open up and contaminate the meat on the lower part of the bird. I won't do that again but I had to try it.
2. I used a fairly mature rooster because that is what I had available to butcher. I am going to experiment more with roosters because I have 7 or 8 more that need processed, but when I get the procedure down I will either use young cockerels or hens, so that the meat is more tender.
3. I did not take the time to find clay soil I wanted to see if it would work with the relatively sandy soil that I have in my yard, if I slathered enough mud on the bird. The mud did dry out and the bird got cooked, but a rather large crack developed allowing part of the moisture to escape. I am planning to try again, with this same soil, but next time I am going to put on one layer of mud add some strips of paper, then put on another layer of mud. this, I think, should prevent the cracking and seal in the moisture as intended.
4. In the story of the beggar, the feathers were "covered in mud" and came right off with the clay vessel when it was broken. When I broke the vessel off, the feather remained and basically had to be plucked off of the already cooked rooster. To make the process work as intended I think I will need to soak the bird in a very thin solution of mud/clay for several hours so that the feathers become part of the clay vessel.
The good
1. The mud did dry out and harden nicely in the oven.
2. The breast meat was above the area that got contaminated, and turned out really tender and pretty tasty.
3. one of my coworkers has a farm with plenty of white clay soil that I can go dig up!