ja, cotton swabs caused scratches. I only use lens wipes and for the tube mirror i use the reci series with a removable lens cap which allows for easy cleaning.
I have learned a lot from your video, I would like to share one more way to make the laser image quality darker that is to use (borax) to mix 1 teaspoon at a boiling temperature of 100 degrees, then use The tool sweeps on the wood surface, then waits for it to dry, then laser