Being light rust it shouldn't be hard to remove.I would get some 4 ought(oooo) steelwool and some light oil.Saturate the SW with the oil and lightly go over the rusted areas.Do not apply to much pressure.You'll remove bluing.When satisfied clean and apply a coat of protective oil.That's one thing I'll never do loan a firearm or vehicle out.You usually get the short end of the stick when you do.

Ruger Redhawk