We have got to go green, AlGore says so! Seriously, in this matter I'd do without the chems.; polish it up one last time, to get everything evenly finished, (also make sure you get all the polish residue off the surfaces, I see a lot there now) and then let nature take its course.
I think you already know that the photo of the British gun that I posted shows a conversion, so with the date (1824) that "David" gave you for the first design of the platform, it may well be that your model barrel is suppossed to represent an original smoothbore.