I sometimes clean the day of and sometimes clean the day before if the part is already sitting in my booth. But me myself and I is the only person in my garage and I have a dedicated home built “booth”. I will give it a quick wipe down with a shop towel the day of to remove any gross dust that may have settled and then tack off right before I spray. If I have to touch the part for any reason it gets recleaned. If I’m ever wiping anything off my exhaust is always on so I can suck out any dust that gets airborne.
I also wash my hands with Dawn before I go out to work to remove any food oil, etc from them.