As for boiling out rust blue, without proper tanks. I came across this on a gunsmith's website, and it worked great for me.
Get a pvc tube, and cut to length needed.
Get a pot to boil water in. I had an old cast iron pot, about 8" in diameter.
Then find a flat piece of metal that will cover the pot.
You should find a flange that the PVC will fit into. This was the most expensive part of the project. I used some 4" pvc since that is what I had laying around. Smaller diameter would be easier to find a flange for. The flange makes it easier to balance the pvc on the pot cover.
Find where the pvc will center on your pot cover, and drill holes.
Once this is done, bring the pot of water with the cover on, to a boil. I did this outside, with a propane burner. Once you have things boiling, set the pvc with the barrel hanging inside over your drilled steam vents. I used a piece of scrap metal, with a hole drilled through, and a wire as a hanger.
Leave your top metal have a bit of venting, to allow the steam to easily circulate in the tube.
Steam for 20 minutes, and you are done.
I simply dropped my smaller parts in the boiling water. You could also make some other smaller pvc container to steam separately if you like.
The steaming would only really need to be for around ten minutes. The extra time I used was for the parts that were actually being boiled, as the temperature was below the steam temperature.
I believe steaming would also eliminate any concern about not having distilled water, as I saw no spots or other problems from steaming, and I have hard water here.
This is the method I used in the Trapdoor Springfield Reborn thread.
PS, you will not have a rough finish, if you do your boil out (steam out) when you have just a very light coat of rust, and use a Brownell's stainless steel buffing wheel made specifically for bluing.