Here is what you need to do the job. Small bottle of instant blue, bottle of rubbing alcohol, 0000 pad of steel wool, liquid dish soap, can of spray lube, and some cue tips.
Use the cue tips and alcohol to degrease the part you want to blue. Pour some of the instant blue into a small cup and dip a small piece of the steel wool pad into it. Apply the instant blue using the steel wool by lightly rubbing it on the part. Keep reapplying until you get the desired coverage. Wash the part with soapy water to neutralize the bluing which is an acid, dry, and then spray with WD40 or G96 lube. HMB