I've been meaning to post this, after searching and reading up on the issue. Not a lot of info out there (or maybe I'm lousy at searching), but in the end it doesn't really matter. IMO, the safe approach is to test the paint so you know what you're dealing with, and can take appropriate precautions.
I purchased a Slingerland duco kit recently, and before starting in with any disassembly/cleaning, I tested the paint. I used a kit recommended by the state as reliable, Leadcheck Instant Test, and the results came back negative. So there's a data point: Not all duco is lead-based. Makes me feel a little better about making a mess.