Interesting post and technique. I had to trim some back ribs to fit my 18.5 WSM and that left me with a bunch of 3-4 bone mini-racks. So I put a different rub on each and smoked them in my mini-WSM. I left one blank - no rub - and only put some peanut oil on it. I was surprised how good it tasted. A rub is not really required for good 'Q and the technique you describe is a good example of that.