Joe,
Looking at my old measures that run steel against cast iron (SAECO and Hollywood) their drums and the measure body surfaces can become smeared with powder residue that comes from such things as ball powder getting between the parts. By using cloth and/or paper towels and various solvents to remove this build up, and a dry lube such as the tungsten disulphide that I mentioned (using a patch to buff it into the clean dry surfaces), a much smoother action is achieved.
The reason that I first tried this goes back to around '99, when I was writing about some of the products that Dave Dohrmann sold, and had sent me samples of, one of which was a small container of tungsten disulphide powder, that he sold, along with moly that he sold for coating bullets. He was the one that told me about how slick it makes powder measures. I tried it, and he was right, so, from time to time, I clean my measures and reapply it. IMO it works very well for this purpose, but the credit for the idea goes to Dave.
As far as the number of rounds that can be fired without cleaning goes, while your barrel maker friend has complete control of the interior finish of the barrels that he shoots in competition, most of us do not, so we must learn to work with what we have.
Close to 15 years ago, I discussed barrel cleaning frequency with George Kelby, when he made it out to a match at the Visalia, CA range. At the time I was following the practice of cleaning between every individual match. George told me that he thought that most benchrest shooters clean more often than is needed, and that every second or third match would do just as well. After that I cleaned every second or third match, depending on the number of sighters shot. Some time after that, I switched to patching once during an agg, with a more thorough cleaning including brushing, at the noon break, and at the end of the day. With patching only, I would not need more than a couple of rounds on the sighter to reassure myself that things were in order for the record, but after brushing, experience taught me that if I did not want to be surprised with an errant shot that at least twice as many on the sighter were required, even if the first two looked good.
It seems to me that the main consideration for determining cleaning method and frequency is the requirement for keeping ahead of the hard carbon situation, and that this can depend on what powder, and even to what pressure one loads. For example, when shooting 133, it is relatively easy to keep things in order with the regimen that I described, but with almost any other powder, more is required. It is not that they are inordinately dirty, but that 133 is so clean. Shooters who switch to some of the new powders that seem to be doing so well, would do well to keep this in mind. What works for 133 will not necessarily do the job for other powders.