Water-soluble flux is an option if you can't use solvents or tolerate no-clean flux residues. Keep in mind, though, that it must be promptly removed, as it's very corrosive. Lead solder isn't terribly dangerous if you wash your hands after handling it.
As far as rosin fluxes go, I like Kester 44. It's active enough to tin corroded surfaces, has an OK smell, and can usually be treated as a no-clean flux (at least for hobby projects).