The Q-tip habit that was quietly scraping my sensor coatings

I was cleaning a customer's 5D Mark III at my bench in Toledo and noticed faint swirl marks under my loupe, which turned out to come from me spinning a dry Q-tip on the sensor for about a year. A retired tech down the street asked what swab I used and just shook his head, then showed me his wet-clean method with a proper squeegee and two drops of Eclipse. I pulled up my old repair log and found four cameras in six months that came back with dust complaints I couldn't explain, all after I'd done a quick dry pass. Now I'm wondering how many of those swirls I blamed on the customer's own cleaning were mine. What's your go-to swab and fluid combo for full frame sensors?