Removing surface rust without ruining paint.

I can second the alu foil, I think it works like a mild abrasive but not abrasive enough to damage chrome etc.
There's old fashioned cleaning product that when disolved in water will remove rust. I used it on an old RD and the chrome and paint came out fine but it dulled the alloy parts. I'll look later for cleaning product, from memory I got it from ebay for £2