I agree with all of those who advise you against cold bluing. The nature of cold blue is that you will wind up with a different coloration for different parts of the gun. There is not as stark a difference on Smith guns as on other manufacturers in my experience, but it will be very dependent upon your ability to get a good polish on the gun parts prior to application of the bluing product. Note that this is a skill that takes quite a while to develop.

If you do choose to refinish the gun, I would suggest a good chelation product to remove all of the remaining bluing as well as all other oxidation on the gun. You can find this type of product in farm stores and on line under a few name brands - quite effective in my limited experience.