Can we focus on what is known about the normal and completely conventional aspects of the burnishing process?
It is a good question, but needs advise on what constructions will actually test for your hypothesis.
For example, the mesh may have worked not be cause it is acting as a "sand paper" with a rough surface peeling off Pd. It may be that there are numerous surface areas that are at a 90 degree position to the stroke and it provides a higher opportunity to "embed" Pd.
So, can a reactor be made that does not use one material section, but perhaps 3 or 4? Place one burnished method A, one method B, perhaps one where the Pd is pressed into flat stock with a hydraulic press, etc. etc. Then using IR measurements, one can see which area of the reactor is "hotter" given the same environmental conditions. This would assist in evaluating different processes of apply the Pd to the substrate.
A second reactor could then be used to possibly check multiple substrates. Apply the Pd via the same method to 4 substrates and place all 4 in the one reactor.
Measure the IR coming from each area.
If this method of testing showed that substrate A with pressed Pd under high pressure always showed more excess heat than other substrates / application methods, then close examination of it would likely be much more informative.
This is not to determine COP, etc. but to quickly identify which application method or which substrate shows a higher active reaction.
Or do you have more specific thoughts on how to go about determining which process is best to use.
One can examine substrates ad hoc, but unless you know it produced excess heat, it would do little good. One could test a lot of null reactors before finding the "lucky" one and then examination may not tell what the actual working mechanism is. A methodical approach of testing substrates versus application methods would seemingly be the way to go. However, you knowledge of your theory would best be suited on designing the parameters of such experiments.