Exactly.

By using a consistent set of props that was what I meant. Take something like Master Airscrew 10 inch props in 4, 5, 6, 7, 8 and 9 inch pitch and run your tests on these. Chances are the lower pitch props won't benifit and may even loose by adding turbulation. At some point around the 5, 6 or 7 inch range I suspect you'll find that dimples, thread, sanded in roughness or some other form of turbulation will produce a reduction in drag in this static situation. But in the air at speed it may not help and may go back to hurting. You'd need some telemetry to test this or a way to move air past your props at about 40 mph to simulate flight operation.

I know turbulation works as I've used it with excellent success on two of my gliders. I also know "it depends" based on trying them on another one with no luck at all.