<<I would not clear coat the frame but would rub with Oxysolv or Rust Mort or some other rust neutralizing stuff, then wax the frame to prevent further rusting. This may discolor the paint though, as it turns any rust black.>>
I would definitely not use the above product, as stated it turns rust black. This in my opinion will destroy the look of the bike, though it will help slow the rusting process. I have used rustmort, or rust seal, POR 15 etc. on bikes many times. For non collectible rusty bikes, it is an easy thing to do to stop the rust. Sometimes on a bike with black paint, it doesn't look terribly bad from a distance, but if the paint is any other color, it looks like someone dripped black die all over it. Chris Ioakimedes Fairfax California