Hi Bill,
I agree with just polishing the brass and then waxing it. I've tried clear coatings over the years on boat related things, using nail polish and clear sprays. You may delay the tarnishing some, but when it comes time to polish it again, you'll have a tough time getting the coating off.
I've found MAAS Polish to be best. It is fast and does a mirror finish. Then the Ren wax. I have "Curator's Wax" from the gun people at the American Historical Foundation. I'll never coat brass with anything else again.
Hope this helps some.
Ev.