I'd have 'em shotpeened. It will restore strength to the steel, plus it will take stress and stress risers out of the leafs (helps keep them from cracking). Most spring shops usually do this as part of the re-arching process, it will produce a "mill" finish unlike sandblasting or bead blasting. If you do this, the spring will have to be disassembled, so you can take the time to replace the pads and keepers. If you're just refinishing, sandblasting with aluminum oxide works pretty good, removes crud but is not nearly as fast cutting (and deep cutting) as silicon nitride, black beauty, slag or silica sand. Doesn't rough the surface excessively.
You can always bead or plastic media, and paint. We had a pretty lengthy discussion on spring rebuilding a while back - I'll dig it up when I get the time (unless someone beats me to it).