Cold blue is relatively cheap compared to other finish options. I have used both Oxpho-blue and 44-40. For your revolver, I'd probably use multiple coats of Oxpho. About $10 from Brownell's, enough to do several applications. Be sure the surface is totally free of any oil or grease (or wax if you use that as a temporary expedient.) I'd use a fine buffing compound to remove as much of the existing surface discoloration as possible to get down to bare metal before starting with the cold blue.

I've only used cold blue for touch up, never an entire firearm, but you have nothing to lose here. Were it mine, I might do the wax thing and live with the "patina."