Went to several proctologists in my lifetime and they all had different routines:
1. My first rectal exam. Just the doctor and me in the room. After an initial talk, he told me to go behind a partition, take off pants and underwear and put on a gown. Then he told me lie on my back at first, then lie on my the side and bring one leg to my chest for the rectal exam. That was my first time and I was really surprised that it didn't hurt at all and it was quick. I was quite young and in fact I thought the doctor had some special powers for being able to do that with no pain. I remember he made a point to tell me to lie on the table normally as I'm sure many people assume they'll be on their stomachs or on all fours. I had no idea what to expect so it was nice that he guided me through it.
2. Just the doctor and me in the room. It was a different setup, with no partition. His desk and exam table were in the same room. After the initial conversation, he told me stand up and take off pants and underwear right in front of him (since there was nowhere else to go). Then he told me to lie on my side and did the rectal exam. After that for some strange reason, he told me to get on my hands and knees on the table and did another rectal exam that way. I don't think that is usual at all and it never happened to me again. Being naked from the waist down and on all fours was very disturbing and a bit humiliating, made worse by the fact that he kept talking to me the whole time. I remember at one time he touched a particular spot and asked for confirmation: "oh, is this what's bothering you?" And kept rubbing that spot as I mumbled an answer. It was very different from the first one, seemed unprofessional and kinda surreal. I only had a light t-shirt on and I was naked and and on all fours on the exam table while a doctor poked my butt.
3. Was led to the exam room by a nurse. Before she left the room, she told me to take off pants and underwear, have a seat on the table, use a drape to cover myself and wait for the doctor. When the doctor came, he sat down right in front of me and we talked while I was already naked, just covered by the unfolded drape. For the rectal exam, he had the kind of table where you kneel at the end and rest your upper body on the table. He positioned himself behind me and did a rectal exam.
4. This one didn't start well. I had been instructed to do two fleet enema the day of the exam and when I arrived, the receptionist asked me if "I was all set with my preparations." I was mortified and upset that everyone in that office knew my business! For the actual exam, it was just me and the doctor in the room. He came in, told me to drop pants and underwear and bend over the table. It was again a new position and similar to the prostate checks I get now. He turned on a lamp directed at me and told me to spread my cheeks for the rectal exam. That was the only time I was asked to do that, also a bit humiliating.
5. The best proctologist I had was unfortunately the one with an ever-present female assistant. I prefer male doctors and dislike anyone else joining, especially women. He had two separate rooms. First we discussed my issues in a regular office setup (desk, computer, etc). Then he told me to go to the actual exam room to get ready. When I got there, I met Trudy, the female assistant, who told me to lower my pants and underwear and lie on my side, with both knees to my chest. Again this was different because I got to keep pants on and just had to lower them. It was a bit weird to lclimb on the table with pants on and also to be exposed to a woman for what seemed an eternity. She draped both sides and basically just left my butt exposed. The doctor came a bit later and did the rectal exam with Trudy in the room. This doctor had a thick accent and made a point to say how "tight" I was and that's why I had problems. Again, a surreal experience to have someone with a finger up your butt discuss your tightness with another person in the room as if we were all in a cocktail party...
So my five rectal exams by proctologists were far from consistent. They each had some unique aspect to them that was never replicated.