I have found cotton balls are not the best thing to apply cold blues.
Another tip:
Don't pour or dip the cold blue directly from the bottle with your applicator, Oxpho-Blue needs to be exposed to air to begin the chemical process and you will contaminate the whole bottle by dipping directly from the bottle and it won't work at all if you dip and redip directly from the bottle.
Go buy a small glass bowel like a salt cellar and dip your cold blue from it.
First polish the metal with 0000 steel wool.
Pour some Oxpho-Blue in your glass container and let it breathe a bit while you are doing this.
Degrease with lighter fluid and a clean white paper towel, let the excess degreaser air dry.
Use another plain white paper towel folded so you have something that looks like a paintbrush.
Start with a very light application of the Oxpho-Blue, just wipe it on and let it set for about 30 seconds, Don't rub it.
Redip your applicator a little wetter and reapply, dab it on, let it sit for thirty seconds and then lightly polish the metal with a clean paper towel.
Keep doing this using progressively wetter applicators, you should begin to see some color after about four applications and it may take eight or more before you get to a color you want.
Do not use steel wool between coats you will just buff the color off before it sets up.
Once you get the color you want wipe the surface dry with a clean paper towel and oil with plain old 3in1 oil, let this sit for at least 24 hours, the cold blue will set up and become durable in this time.
You may now lightly polish with the 0000 steel wool to obtain the luster you want.
I have been using Oxpho-Blue for touch up work since the stuff first came out and this technique has always worked and produced a durable finish.
Birchwood Casey Aluma-Black is what you want for the AR receiver innards and the technique works exactly the same with this stuff too. HTH
