Looks like you are getting plenty of good advice here. I don't want to add confusion, but will add a couple of alternatives in case you don't find some of what has been suggested. For polishing brass after the sanding is done, I prefer Simichrome polish. It works equally well on brass and silver. I've been using it for over 50 years with great results. We used it to polish brass uniform buttons that were popular on law enforcement uniforms back in the day. Been using it ever since.
For aging brass, I like Brownell's Oxpho Blue, but most cold bluing solutions will probably work. It's not rocket science, lol. Actually, a dirty cleaning patch (one with black powder residue) will also work. I can't help you on the browning solution, but I don't think you'd be out much to try. It certainly won't hurt anything.
Good luck with the build, and keep posting the pictures. We all enjoy build pictures, especially now that we are pretty much all shut-ins.
For aging brass, I like Brownell's Oxpho Blue, but most cold bluing solutions will probably work. It's not rocket science, lol. Actually, a dirty cleaning patch (one with black powder residue) will also work. I can't help you on the browning solution, but I don't think you'd be out much to try. It certainly won't hurt anything.
Good luck with the build, and keep posting the pictures. We all enjoy build pictures, especially now that we are pretty much all shut-ins.