No cold blue will match either the look of, or the durability of a professionally done hot blue. BUT, you can do a reasonable cold blue job at home. Unless you are just doing a touch up, you can remove the old blue chemically...I think Birchwood markets the stuff, and any reasonably stocked gunshop should carry either the Birchwood, or another brand. It's very effective and easy to use. After that you'll need to work on any remaining rust or pitting. As the guys have mentioned, just make sure you don't use anything so abrasive that it leaves marks worse than the ones you started out with. Just my opinion, but the best cold blue I've found is Brownells Oxpho Blue. It's supposed to penetrate dirt and oil, but it's best to get your metal as squeaky clean as possible. Again, Birchwood and a few others market a special cleaning compound for that purpose, but if I recall, it's just carbon tetrachloride. Oxpho Blue may be available elsewhere, but the only Canadian source I've found is Wholesale Sports...the cream stuff as already recommended. Use a hair dryer or heat gun to make the metal almost too hot to handle before you apply the the blue. Follow the directions that come with it, and apply as many coats as you need to get the depth of color you want. A few supplies and a bit of patience, along with a good measure of elbow grease will give you results you should be pleased with.