Hi Roger,
I've used artists hog haired brushes for years for cleaning this and that and felt a bit dumb for not thinking of it when Mr Howard suggested using one for getting in amongst the keys and tone holes.
They are relatively cheap and if you get oil on it from the rods a quick bit of lighter fluid cleans it up nicely. I use a size 10 but a smaller one might be useful as well.
I'd say it works well for cleaning but polishing, I think that might be pushing it, for that you could always try wrapping a corner of your polishing cloth on the other end of the brush handle and see how far that gets you.
All the best,
Chris.