If the Bronco spent time on the rails, the rust could be from rail dust. Is it on the paint or under it. If it is on the paint, a good automotive clay will remove it. Had to detail an F150 because of this years ago. Very nice! Thanks for sharing.
If you haven’t driven a Bronc yet, I highly recommend it. They really are a different animal. I may have gone gladiator if I hadn’t driven one with the soft top.
Good luck, brother.