I've used q-tips in the past, and cotton rag/ patches to apply the cold blue, but the dipping really gives the parts a nice dark blue / black color with out having to re-apply a couple times. So I like the dipping part, I just don't like the tossing out the old after I dipped a few parts.
I guess part of my question should have been if dipping a part in would contaminate the cold blue solution so tossing it out is the proper thing to do if it's not used in a short amount of time.
Each time I'm tempted to pour it back into the bottle, but right now I think I'll keep the used solution in a separate container and see if it keeps doing the trick. I'm not talking a ton of it, just a couple cap-fulls... but it's a lot more than using a q-tip even after 3 applications LOL
I want to stay away from rust bluing for now... and just stick with the cold blue