Old guy taught me the wire brush trick on a zero clearance unit

Last fall I was doing a routine sweep out in Rockford. Lady had a zero clearance fireplace, pre-fab box. I get up top, start with the poly brush, and this 70 year old homeowner comes out and watches me for a minute. He says "you're gonna scratch the hell out of that flue with that thing." I told him it's standard. He walks to his shed, comes back with a worn down steel wire brush that had the bristles bent flat. Says "run this dry, light pressure. Takes longer but it won't gouge the liner." I figured he was full of it, but I tried it after my first pass. That brush grabbed the creosote way better on the tight spots. No scratches, no metal shavings. He said he did chimneys for 35 years back in the 70s and 80s, before all the fancy gear. I still use poly for big masonry flues, but for those pre-fab units I keep a beat up wire brush in the truck now. Anyone else got a trick from an old timer that beat the modern stuff?