For those who prefer a liquid touch-up blueing. Blues instantly to produce a rich blueing that will not rub off or discolor.

Remove all oil, grease, or dirt from surface to be blued by cleaning with G96 Gun Degreaser.  Pitted or rusted surfaces should be sanded lightly with emery cloth or steel wool.  Apply a small amount of G96 Gun Blue liquid with a clean patch.  After blueing is achieved (after turning greyish, usually within 15-30 seconds), neutralize area with water.  Wipe dry and apply a protective coating of G96 Gun Treatment or G96 Gun oil or G96 Synthetic CLP Gun Oil for a long lasting lustrous finish.  Better penetration is achieved if metal is slightly warm.  Wash hands after use.