Bighorn will hopefully reply to this question.
Looked to me like he used a big pot with water in the bottom then nestled a slightly smaller pot inside and steamed away. But, I was enjoying a cool drink in my chair some distance away from the cook table.
On the breakfast burreto's also super neat and good, they were made at home, double wrapped in foil and frozen, in camp taken out of the cooler, then placed in the coleman fold up stove top ovens. While we sat around drinking coffee, they were heated through and through - then handed out. No mess, no dish washing - just unwrap and eat. Another great breakfast when you want to avoid time in the kitchen and get on the water.
All in all, most meals were quick to prepare in camp, not much dish washing and tasty.
All in all, BigHorn's river team were as efficient on the river at cooking as I have seen. Lot's of ideas and I have been river tripping for decades.