The important thing IMO is to test it like you use it. Try to simulate the actual conditions.
For a drying/buffing/etc. towel, that'd be dry- just fold the towel however you use it and apply the sort of pressure you would use for the given task. When testing a drying towel, I usually do actually dry a wet CD with it.
For wash media, it gets a little more complicated- I make sure the media being tested is thoroughly wet with wash solution, just as it would be when doing the wash, and I first dunk the CD in the wash solution. Again, apply the same sort of pressure you'd use when doing the job for real. Heh heh, a dry sheepskin mitt or BHB will mar something awful, but, with any luck, it'll be a different story when the shampoo mix is employed.
When testing brushes, try to test the *whole* brush. One nasty bristle, like the few bad ones I had on the TOL BHBs, can do a lot of damage and your test won't warn you if you don't test that section of the brush.
Inspect BHBs for adhesive contamination of the bristles. And if the adhesive covers a significant portion of the bristles (down by the handle), keep an eye on it as it can break loose over time and deposit hard adhesive throughout the bristles....and that stuff can seriously mar automotive paint (gee, as how I know
).
I find that (per usual) I can best inspect the CD under incandescent light, and I use a magnifying visor too, which is great for all sorts of things...
