I just use whatever is available at the local gun store. I think it is more important that the barrel be well degreased. Dawn detergent works as well as anything. Otherwise, you need to wipe it down good with acetone. I would go with the Dawn first. After that, the barrel will rust up pretty good on its own. The cold blue is just to give you black oxide undertones when you are done. The next day after applying the tincture of iodine, you will have lots of red rust that needs to be scrubbed back. The better you degrease, the more even the rusting and the final finish will be. Of course, sometimes you don't want even.
