Alcohol pads are the worst thing you can put on an old coating, they eat right through it and you never get that back. I keep a bulb blower and a soft brush handy for dust first, then breath and a clean microfiber for anything stuck on there. Rubbing alcohol only touches metal or glass with no coating, never the front element.

Figure out what he meant by "fit-up first" though, because that can mean a lot of things depending on what you're building. Was he talking about your root gap, your joint alignment, bevel prep, or was it more about how the parts sit together before you even start? That distinction matters a ton, because if your fit-up is off by a hair, no amount of grinding is gonna save that weld. And how did you test it on those three vessels, did you actually measure the difference or just eyeball it and feel better about the work? Three vessels is a small sample, and half the rework going away could just mean you got lucky with easier jobs that month. I'm not knocking the guy, old-timers usually know something, but I'd want to know if that fix holds up when you're back on the ugly stuff.