I have my enlarger set up in level 10 dust free clean room with atomic level particle cleaner at all air vents. (just kidding....)
I'm not an old timer but I have been printing for about 6 months in regular residential setup. My enlarger is 40+ year old Omega D-II. When I got this enlarger, I've taken it apart and cleaned every part of enlarger using wet rag, compressed air, and vacuum cleaner. Before I set the negative in carrier, I clean it with soft lint free cloth, sandwich it, then use compressed air to blow dust. Then print. I see dust maybe 1 out of 20 prints and only very small ones. If I omit cleaning the negative and blow part, then I see it 50% of times.
I have yet, another enlarger in my garage going through the cleaning process. With this one, I have to scrape off all the lose paint, refinish and paint. Then dust, then assemble.
Can you identify the kind of dust you see? Is it coming from enlarger itself?