Now for the rust blueing! Once all parts are to be blued are polished out to either 320 grit or 400 they have to be well cleaned as any oil left on the parts will spoil the blueing. For this I use lacquer thinner and once cleaned I do not handle the parts or barrels with out using clean gloves. Since rust blue is really rust turned into black iron oxide we do not want it to get into the bores as it will etch them and result in at best a dark bore. Some people recomend using wood plugs to plug the bore but since this rust blue involves boiling the barrels I do not like this idea. If a plug blows out you could get a face full of boiling water. In addition to that there is no way to check to ensure that no water has seeped into the bore other then removing the plugs.
What I have had very good results with is to paint the bores. Any good water proof spray paint will work for this. Spray from both ends and make sure the bores are completely covered. If some paint gets where you do not want it you can clean it off with lacquer thinner. Once the barrels are blued just soak them in lacquer thinner and scrub with a brush to remove the paint.
For the blueing it self I use Great American Rust Blue which Browenells carries. You swab on one coat and waite for a couple of hours and apply the next coat. Several hours later your parts will be red and motteled black with rust and look like HELL! This is fine and the next day boil the barrels and parts in clean water, card them off with clean 0000 steel wool. (Wash the steel wool in lacquer thinner as it is coated with oil so it will not rust)
Apply another coat of the rust blue solution and let the barrels and parts set in a damp area over night if you want a saten finish or no more then eight to ten hours for a shinier finish. The longer you waite between coats the duller the finish will be as the rust blue has more time to etch deeper into the metal.
Once you have the depth of blue you want, this will in most cases take five to ten cycles, (bioling for 15 min., carding boiling until hot then applying the next coat) it is time to boil the parts for around half an hour to stop the rusting action and then soak them for half an hour in water displacing oil. Once this is done wash everything again in lacquer thinner scrub out the paint in the bores and give every thing a light coat of linseed oil after buffing out with 0000 steel wool. If I have confused you please ask questions, the process though timely is really simple and you will not find a tuffer blueing with any other process.